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Use of GLP-1 Receptor Agonists and
Occurrence of Thyroid Disorders:
a Meta-Analysis of Randomized
Controlled Trials
Weiting Hu
1
, Rui Song
1
, Rui Cheng
2
, Caihong Liu
3
, Rui Guo
3
, Wei Tang
2
, Jie Zhang
2
,
Qian Zhao
2
, Xing Li
2
*and Jing Liu
2
*
1
The Second Clinical Medical College, Shanxi Medical University, Taiyuan, China,
2
Department of Endocrinology, Second
Hospital of Shanxi Medical University, Taiyuan, China,
3
Department of Physiology, Shanxi Medical University, Taiyuan, China
The association between glucagon-like peptide-1 (GLP-1) receptor agonists and the risk
of various kinds of thyroid disorders remains uncertain. We aimed to evaluate the
relationship between the use of GLP-1 receptor agonists and the occurrence of 6 kinds
of thyroid disorders. We searched PubMed (MEDLINE), EMBASE, the Cochrane Central
Register of Controlled Trials (CENTRAL) and Web of Science from database inception to
31 October 2021 to identify eligible randomized controlled trials (RCTs). We performed
meta-analysis using a random-effects model to calculate risk ratios (RRs) and 95%
confidence intervals (CIs). A total of 45 trials were included in the meta-analysis.
Compared with placebo or other interventions, GLP-1 receptor agonists’use showed
an association with an increased risk of overall thyroid disorders (RR 1.28, 95% CI 1.03-
1.60). However, GLP-1 receptor agonists had no significant effects on the occurrence of
thyroid cancer (RR 1.30, 95% CI 0.86-1.97), hyperthyroidism (RR 1.19, 95% CI 0.61-
2.35), hypothyroidism (RR 1.22, 95% CI 0.80-1.87), thyroiditis (RR 1.83, 95% CI 0.51-
6.57), thyroid mass (RR 1.17, 95% CI 0.43-3.20), and goiter (RR 1.17, 95% CI 0.74-1.86).
Subgroup analyses and meta-regression analyses showed that underlying diseases, type
of control, and trial durations were not related to the effect of GLP-1 receptor agonists on
overall thyroid disorders (all P
subgroup
> 0.05). In conclusion, GLP-1 receptor agonists did
not increase or decrease the risk of thyroid cancer, hyperthyroidism, hypothyroidism,
thyroiditis, thyroid mass and goiter. However, due to the low incidence of these diseases,
these findings need to be examined further.
Systematic Review Registration: PROSPERO https://www.crd.york.ac.uk/prospero/,
identifier: CRD42021289121.
Keywords: GLP-1 receptor agonists, thyroid disorders, thyroid cancer, meta-analysis, randomized controlled trials
Frontiers in Endocrinology | www.frontiersin.org July 2022 | Volume 13 | Article 9278591
Edited by:
Johannes Wolfgang Dietrich,
Ruhr University Bochum, Germany
Reviewed by:
Daniel Quast,
St. Josef-Hospital Bochum, Germany
Simone Wajner,
Federal University of Rio Grande do
Sul, Brazil
Stephen Bain,
Swansea University, United Kingdom
Trevor Edmund Angell,
University of Southern California,
United States
*Correspondence:
Jing Liu
13934663905@163.com
Xing Li
13503504180@163.com
Specialty section:
This article was submitted to
Thyroid Endocrinology,
a section of the journal
Frontiers in Endocrinology
Received: 25 April 2022
Accepted: 13 June 2022
Published: 11 July 2022
Citation:
Hu W, Song R, Cheng R, Liu C, Guo R,
Tang W, Zhang J, Zhao Q, Li X and
Liu J (2022) Use of GLP-1 Receptor
Agonists and Occurrence of Thyroid
Disorders: a Meta-Analysis of
Randomized Controlled Trials.
Front. Endocrinol. 13:927859.
doi: 10.3389/fendo.2022.927859
SYSTEMATIC REVIEW
published: 11 July 2022
doi: 10.3389/fendo.2022.927859
INTRODUCTION
Thyroid diseases are common in some metabolic disorders, such
as diabetes mellitus (DM) and obesity. Thyroid dysfunction (TD)
and DM are closely linked. A high prevalence of TD has been
reported among both type 1 DM (T1DM) and type 2 DM
(T2DM) patients (1,2). Although the mechanism is unknown,
epidemiological studies have indicated that obesity and T2DM
are associated with increased risks of several cancers, including
thyroid cancer (3–5). Furthermore, insulin resistance and
hyperinsulinemia can lead to goiter, proliferation of thyroid
tissues, and an increased incidence of nodular thyroid disease
(6). In addition to the effects of the disease itself, some
antidiabetic drugs can impact the hypothalamic–pituitary–
thyroid (HPT) axis and thyroid function. For example,
multiple studies have demonstrated that metformin can inhibit
the growth of thyroid cells and different types of thyroid cancer
cells, and metformin therapy has been associated with a decrease
in the levels of serum thyroid-stimulating hormone (TSH) (7).
Thiazolidinediones can induce thyroid-associated
ophthalmopathy (8,9). Recently, the relationship between
glucagon-like peptide-1 (GLP-1) receptor agonists and thyroid
cancer has attracted attention, but there is still controversy.
GLP-1 is an amino acid peptide hormone secreted by L cells
of the gastrointestinal mucosa that promotes insulin secretion,
suppresses glucagon secretion, and delays gastric emptying (10).
Rodent studies have shown that the GLP-1 receptor agonist
liraglutide can activate the GLP-1 receptor on thyroid C cells,
leading to the release of calcitonin with a dose-dependent effect
on the pathology of C cells (11). Some animal models have
proven that exenatide or liraglutide treatment is related to the
abnormal appearance of thyroid C cells, with gradual
development of hyperplasia and adenomas (12,13). Moreover,
a study found that patients treated with exenatide had an
increased risk of thyroid cancer by examining the US Food
and Drug Administration’s database of reported adverse events
(14). However, the results of A Long Term Evaluation
(LEADER) trial that followed for 3.5-5 years showed no effect
of GLP-1 receptor activation on human serum calcitonin levels,
C-cell proliferation or C-cell malignancy (15). Nevertheless,
GLP-1 receptor agonists are not recommended in patients with
a personal or family history of medullary thyroid cancer or type 2
multiple endocrine neoplasia.
GLP-1 receptor agonists, a new type of antidiabetic drug for
treating T2DM in recent years, with additional benefits of weight
loss and blood pressure reduction (16). Although many large
randomized controlled trials (RCTs) of GLP-1 receptor agonists
have identified the obvious benefits of GLP-1 receptor agonists
on cardiovascular and renal outcomes in patients with DM or
obesity (17–20), the association between GLP-1 receptor agonists
and various thyroid disorders remains controversial. In addition,
considering that thyroid disorders are common in some
metabolic diseases such as DM and obesity, we conducted this
study. Thus, by comparing GLP-1 receptor agonists with placebo
or other antidiabetic drugs, we conducted a meta-analysis of all
available RCT data to evaluate the relationship between the use
of GLP-1 receptor agonists and the occurrence of various kinds
of thyroid disorders.
METHODS
Data Sources and Searches
We searched PubMed (MEDLINE), EMBASE, Cochrane Central
Register of Controlled Trials (CENTRAL) and Web of Science
from database inception to 31 October 2021 to identify eligible
RCTs without restriction of language or publication period. The
search terms used were “glucagon-like peptide 1 receptor
agonist”,“exenatide”,“liraglutide”,“dulaglutide”,“lixisenatide”,
“semaglutide”,“albiglutide”,“taspoglutide”,“loxenatide”,
“diabetes mellitus”,“obesity”and “randomized controlled
trial”. In addition, we manually scanned the ClinicalTrials.gov
web and reference lists from established trials and review articles.
Study Selection
The trials we included met the following criteria: (1) RCTs that
compared GLP-1 receptor agonist with a placebo or active control
(other antidiabetic drugs or insulin), (2) patients with type 2
diabetes, type 1 diabetes, prediabetes, overweight or obesity, (3)
with durations of at least 24 weeks,and (4) reported the occurrence
of at least one case of various thyroid disorders as adverse events.
We excluded duplicate reports, conference abstracts, letters, case
reports, editorials, articles without treatment-emergent adverse
events, and animal experimental studies.
Data Extraction and Quality Assessment
Two investigators (Hu and Song) independently extracted the
following data by reviewing the full text of each study: first
author, year of publication, Clinical Trial Registration Number
(NCT ID), trial duration, patient characteristics, sample size,
intervention (type of GLP-1 receptor agonist), comparators, and
outcomes of interest. Any discrepancies were resolved by
consensus or by the third reviewer (Chen). The primary
outcome was the incidence of overall thyroid disorders, and
the secondary outcomes included the incidence of goiter,
hyperthyroidism, hypothyroidism, thyroiditis, thyroid mass,
and thyroid cancer. When multiple reports from the same
population were retrieved, the most complete or recently
reported data were used. If thyroid-related events were not
reported in publication, these data were extracted from the
‘Serious Adverse Events’portion of ClinicalTrials.gov.
The quality of each included RCT was assessed by the
Cochrane Risk-of-Bias Tool 1.0. The Jadad scale was also used
to quantify the study quality. Two authors assessed the risk of
bias for each study through five aspects: random sequence
generation, allocation concealment, blinding, incomplete
outcome data and selective reporting.
Statistical Analysis
Dichotomous outcomes were analyzed by risk ratios (RRs) and
95% confidence intervals (CIs) using the DerSimonian and Laird
random-effects model. We assessed heterogeneity between the
Hu et al. GLP-1RAs and Thyroid Disorders
Frontiers in Endocrinology | www.frontiersin.org July 2022 | Volume 13 | Article 9278592
included studies using the I² statistic, where I
2
values of 25%,
50%, and 75% indicated low, medium, and high heterogeneity,
respectively. Subgroup analyses were conducted according to the
type of underlying diseases, type of control, and trial duration.
Between-subgroup heterogeneity was assessed by c
2
tests and
meta-regression. All of the above analyses were performed using
Stata software 13.0 (Stata Corp). A p value < 0.05 was considered
statistically significant.
RESULT
Study Search and Study Characteristics
A total of 16,201 records were identified by retrieving the
aforementioned databases. Excluding duplicates and reviewing
titles and abstracts, 301 studies were read the full text. After
retrieving the full text and searching on ClinicalTrials.gov, the
final analysis included 45 RCTs reported in 45 publications with
94063 participants (17–61). Although the data from the two articles
were presented together on ClinicalTrials.gov (62), due to the
differences in population characteristics and follow-up time, we
considered them separately and regarded them as two independent
trials (24,25). The search and selection process is summarized in
Figure 1.The characteristicsof these includedstudies are detailedin
Table 1 and Table S1. Across the 45 trials, trial duration ranged
from 26 to 360 weeks. Of all the participants, 29,348 (55.8%) were
men in the experimental group, and 24121 (58.2%) were men in the
control group. The mean age of study participants ranged from41.6
to 66.2 yearsold in experimentalgroups and 41.4 to 66.2 years old in
control groups. Mean patient body mass index (BMI) ranged from
24.5 to 39.3kg/m2 in experimental groups and24.4 to 39.0 kg/m2 in
control groups.
Risk of Bias Evaluation
The studies included in this analysis provide information about
random sequence generation, allocation concealment,
participant blindness, personnel, outcome evaluation and
selective reporting. Figure S1 reports the risk details of
deviation assessment. (Figure S1 in Appendix) 29 trials had a
Jadad scale of 4 or 5, and others were scored ≤3.
Incidence of Thyroid Disorders With All
GLP-1 Receptor Agonists
As is shown in Figure 2, this meta-analysis included 52600
patients in the GLP-1 receptor agonist group and 41463 patients
in the control group. The event rate in the GLP-1 receptor
agonist group (0.39%) was higher than in the control group
(0.31%). Compared with placebo or other interventions, GLP-1
receptor agonist increased the risk of overall thyroid disorders by
28% (RR 1.28, 95% CI 1.03-1.60; p = 0.027), with no statistically
significant between-study heterogeneity (I
2
= 0.0%). The funnel
plot for this analysis indicated no significant publication bias
(Figure S2).
GLP-1 receptor agonists versus placebo or other interventions
had no significant effects on the occurrence of thyroid cancer (RR
1.30, 95% CI 0.86-1.97, p = 0.212; I
2
=0.0%;Figure S3),
hyperthyroidism (RR 1.19, 95% CI 0.61-2.35, p = 0.608; I
2
=
0.0%; Figure S4), hypothyroidism (RR 1.22, 95% CI 0.80-1.87, p =
0.359; I
2
= 0.0%; Figure S5), thyroiditis (RR 1.83, 95% CI 0.51-
6.57, p = 0.353; I
2
= 0.0%; Figure S6), thyroid mass (RR 1.17, 95%
CI 0.43-3.20, p = 0.759; I
2
= 0.0%; Figure S7), and goiter (RR 1.17,
95% CI 0.74-1.86, p = 0.503; I
2
= 0.0%; Figure S8).
Incidence of Thyroid Disorders With
Different GLP-1 Receptor Agonists
Among all 45 enrolled trials, 18 trials including 24787 patients
used liraglutide as the experimental agent. Compared with
placebo or other interventions, treatment with liraglutide
increased the risk of overall thyroid disorders by 37% (RR
1.37, 95% CI 1.01-1.86, p = 0.044; Figure 3), and no
statistically significant between-study heterogeneity was
observed (I
2
= 0.0%, p = 0.933).
Moreover, another 5 trials including 13281 patients provided
information about the risk of thyroid disorders in patients
treated with dulaglutide. This result showed that compared
with placebo or other interventions, dulaglutide significantly
increased the incidence of overall thyroid disorders by 96%
(RR 1.96, 95% CI 1.11-3.45, p = 0.020; Figure 3), and no
statistically significant between-study heterogeneity was
observed (I
2
= 0.0%, p = 0.965).
However, no effect against overall thyroid disorders was
found for other GLP-1 receptor agonists. There were 11 studies
including 15401 patients that regarded semaglutide as the
experimental agent, and the pooled RR of overall thyroid
disorders in patients receiving semaglutide versus other
interventions was 0.75 (95% CI 0.35‐1.57; Figure 3). Whether
oral semaglutide or subcutaneous semaglutide, the results
showed that they had no significant effects on the occurrence
of overall thyroid disorders (Figure S9 and Figure S10). There
were 5 studies including 8895 patients that regarded lixisenatide
as the experimental agent, and the pooled RR of overall thyroid
disorders in patients receiving lixisenatide versus other
FIGURE 1 | Summary of trial selection.
Hu et al. GLP-1RAs and Thyroid Disorders
Frontiers in Endocrinology | www.frontiersin.org July 2022 | Volume 13 | Article 9278593
TABLE 1 | Baseline characteristics of included studies.
Study Clinical Trial
Registration
Number
Trial Duration
(week)
Interventions Events/Patients (N) Age (years) Man (N, %) BMI (kg/m
2
) Jadad
score
Experimental Control Experimental Control Experimental Control Experimental Control Experimental Control
Unger et al., 2022 (21) NCT02730377 105 Liraglutide OAD 1/996 0/995 57.6 (11.0) 57.1
(10.7)
520 (52.2) 524
(52.7)
33.2 (7.2) 33.7
(7.6)
2
Garveyet al 2020 (22) NCT02963922 60 Liraglutide Placebo 1/198 0/198 55.9 (11.3) 57.6
(10.4)
90 (45.5) 99 (50.0) 35.9 (6.5) 35.3
(5.8)
4
Wadden et al., 2020
(23)
NCT02963935 60 Liraglutide Placebo 1/142 0/140 45.4 (11.6) 49.0
(11.2)
23 (16.2) 24 (17.1) 39.3 (6.8) 38.7
(7.2)
4
le et al., 2017 (24) NCT01272219 172 Liraglutide Placebo 3/1505 3/749 47.5 (11.7) 47.3
(11.8)
364 (24.0) 176
(23.0)
38.8 (6.4) 39.0
(6.3)
4
Pi-Sunyer et al., 2015
(25)
NCT01272219 68 Liraglutide Placebo 1/959 0/487 41.6 (11.7) 41.5
(11.5)
158 (16.5) 97 (19.9) 37.5 (6.2) 37.4
(6.2)
4
Zang et al., 2016 (26) NCT02008682 26 Liraglutide Sitagliptin 0/183 1/184 51.7 (10.7) 51.4
(11.0)
102 (55.7) 117
(63.6)
27.3 (3.4) 27.2
(4.0)
2
Ahren et al., 2016 (27) NCT02098395 26 Liraglutide Placebo 2/625 0/206 43.3 42.7 288 (46.1) 94 (45.6) 28.9 28.9 4
Mathieu et al., 2016
(28)
NCT01836523 52 Liraglutide Placebo 0/1042 1/347 43.7 43.4 496 (47.6) 167
(48.1)
29.4 29.8 4
Marso et al., 2016
(20)
NCT01179048 240 Liraglutide Placebo 77/4668 54/
4672
64.2 (7.2) 64.4
(7.2)
3011 (64.5) 2992
(64.0)
32.5 (6.3) 32.5
(6.3)
4
Davies et al., 2015
(29)
NCT01272232 68 Liraglutide Placebo 1/634 1/212 55.0 54.7 328 (51.7) 97 (45.8) 37.1 37.4 4
Gough et al., 2014
(30)
NCT01336023 52 Liraglutide
IDegLira
Degludec 2/414
0/833
0/413 55.0 (10.2)
55.1 (9.9)
54.9
(9.7)
208 (50.2)
435 (52.2)
200
(48.4)
31.3 (4.8)
31.2 (5.2)
31.2
(5.3)
3
Wadden et al., 2013
(31)
NCT00781937 56 Liraglutide Placebo 3/212 0/210 45.9 (11.9) 46.5
(11.0)
34 (16.0) 45 (21.4) 38.2 (6.2) 37.5
(6.2)
4
Seino et al., 2010 (32) NCT00393718 52 Liraglutide Glibenclamide 1/268 0/132 58.2 (10.4) 58.5
(10.4)
183 (68.3) 86 (65.2) 24.5 (3.7) 24.4
(3.8)
4
Pratley et al., 2010
(33)
NCT00700817 78 Liraglutide Sitagliptin 1/446 0/219 55.5 55.0 232 (52.0) 120
(55.0)
32.9 32.6 2
Nauck et al., 2009
(34)
NCT00318461 104 Liraglutide Glibenclamide
Placebo
6/724 2/242
0/121
56.7 57.3
56.0
422 (58.3) 139
(57.4)
72 (59.5)
30.8 31.2
31.6
4
Garber et al., 2009
(35)
NCT00294723 104 Liraglutide Glibenclamide 6/498 0/248 52.9 53.4 238 (47.8) 133
(53.6)
33.0 33.2 3
Hernandez et al.,
2018 (36)
NCT02465515 130 Albiglutide Placebo 0/4731 1/4732 64.1 (8.7) 64.2
(8.7)
3304 (70.0) 3265
(69.0)
32.3 (5.9) 32.3
(5.9)
5
Home et al., 2015 (37) NCT00839527 52 Albiglutide Pioglitazone
Placebo
5/271 9/277
2/115
54.5 (9.5) 55.7
(9.4)
55.7
(9.6)
135 (49.8) 148
(53.4)
70 (60.9)
32.4 (5.5) 32.2
(5.7)
31.8
(4.9)
3
Ahren et al., 2014 (38) NCT00838903 164 Albiglutide Sitagliptin
Glibenclamide
Placebo
1/302 2/302
0/307
0/101
54.3 (10.1) 54.3
(9.8)
54.4
(10.0)
56.1
(10.0)
135 (44.7) 139
(46.0)
158
(51.5)
50 (49.5)
32.7 (5.6) 32.5
(5.4)
32.5
(5.5)
32.8
(5.4)
2
Leiter et al., 2014 (19) NCT01098539 60 Albiglutide Sitagliptin 1/249 0/246 63.2 (8.4) 63.5
(9.0)
136 (54.6) 130
(52.8)
30.4 (5.5) 30.4
(5.8)
4
(Continued)
Hu et al. GLP-1RAs and Thyroid Disorders
Frontiers in Endocrinology | www.frontiersin.org July 2022 | Volume 13 | Article 9278594
TABLE 1 | Continued
Study Clinical Trial
Registration
Number
Trial Duration
(week)
Interventions Events/Patients (N) Age (years) Man (N, %) BMI (kg/m
2
) Jadad
score
Experimental Control Experimental Control Experimental Control Experimental Control Experimental Control
Holman et al., 2017
(18)
NCT01144338 360 Exenatide Placebo 23/7356 16/
7396
61.8 (9.4) 61.9
(9.4)
4562 (62) 4587(62) 31.8 31.7 5
Gallwitz et al., 2012
(39)
NCT00359762 216 Exenatide Glimepiride 0/490 4/487 56.0 (10.0) 56.0
(9.1)
272 (55.5) 252
(51.7)
32.6 (4.2) 32.3
(3.9)
2
Bergenstal et al., 2010
(40)
NCT00637273 26 Exenatide Sitagliptin
Pioglitazone
0/160 1/166
0/165
52.4 (10.4) 52.2
(10.5)
53.0
(9.9)
89 (55.6) 86 (51.8)
79 (47.9)
32.0 (5.0) 32.0
(5.0)
32.0
(6.0)
3
Wang et al., 2019 (41) NCT01648582 56 Dulaglutide Glargine 8/505 2/250 54.8 55.4 278 (55.0) 139
(55.6)
26.8 26.7 2
Gerstein et al., 2019
(42)
NCT01394952 336 Dulaglutide Placebo 26/4949 14/
4952
66.2 (6.5) 66.2
(6.5)
2643 (53·4) 2669
(53·9)
32.3 (5.7) 32.3
(5.8)
5
Chen et al., 2018 (43) NCT01644500 26 Dulaglutide Glimepiride 2/478 0/242 53.2 52.0 261 (54.6) 130
(53.7)
26.0 25.7 4
Weinstock et al., 2015
(44)
NCT00734474 104 Dulaglutide Sitagliptin
Placebo
3/606 0/315
0/177
54.0 54.0
55.0
280 (46.2) 151
(48.0)
90 (51.0)
31.0 31.0
31.0
5
Giorgino et al., 2015
(45)
NCT01075282 78 Dulaglutide Glargine 1/545 0/262 56.5 57.0 280 (51.4) 134
(51.0)
31.5 32.0 2
Rosenstock et al.,
2016 (46)
NCT02058147 30 Lixisenatide
iGlarLixi
Glargine 0/469
0/234
1/467 58.7 (8.7)
58.2 (9.5)
58.3
(9.4)
133 (56.8)
222 (47.3)
237
(50.7)
32.0 (4.4)
31.6 (4.4)
31.7
(4.5)
2
Pfeffer et al., 2015 (47) NCT01147250 225 Lixisenatide Placebo 2/3034 3/3034 59.9 (9.7) 60.6
(9.6)
2111 (69.6) 2096
(69.1)
30.1 (5.6) 30.2
(5.8)
5
Bolli et al., 2014 (48) NCT00763451 112 Lixisenatide Placebo 2/322 0/160 55.0 58.2 143 (44.4) 72 (45.0) 32.6 32.4 5
Ahren et al., 2013 (49) NCT00712673 76 Lixisenatide Placebo 1/510 1/170 54.7 55.0 212 (41.6) 81 (47.6) 32.9 33.1 4
Riddle et al., 2013
(50)
NCT00715624 125 Lixisenatide Placebo 1/328 0/167 57.4 (9.5) 56.9
(9.8)
146 (44.5) 82 (49.1) 31.9 (6.2) 32.6
(6.3)
5
Wilding et al., 2021
(51)
NCT03548935 75 Semaglutide Placebo 1/1306 0/655 46.0 (13.0) 47.0
(12.0)
351 (26.9) 157
(24.0)
37.8 (6.7) 38.0
(6.5)
4
Wadden et al., 2021
(52)
NCT03611582 75 Semaglutide Placebo 1/407 0/204 46.0 (13.0) 46.0
(13.0)
92 (22.6) 24 (11.8) 38.1 (6.7) 37.8
(6.9)
5
Yamada et al., 2020
(53)
NCT03018028 57 Semaglutide
Liraglutide
Placebo 1/146
0/48
0/49 59.7
59.0
59.0 112 (76.7)
39 (81.3)
40 (81.6) 25.8
26.9
25.1 5
Husain et al., 2019
(54)
NCT02692716 87 Semaglutide Placebo 2/1591 2/1592 66.0 (7.0) 66.0
(7.0)
1084 (68.1) 1092
(68.6)
32.3 (6.6) 32.3
(6.4)
5
Rosenstock et al.,
2019 (55)
NCT02607865 83 Semaglutide Sitagliptin 0/1396 1/467 58.0 58.0 746 (53.4) 238
(51.0)
32.5 32.5 3
Pratley et al., 2019
(56)
NCT02863419 57 Semaglutide
Liraglutide
Placebo 2/285
1/284
0/142 56.0 (10.0)
56.0 (10.0)
57.0
(10.0)
147 (51.6)
149 (52.5)
74 (52.1) 32.5 (5.9)
33.4 (6.7)
32.9
(6.1)
4
Aroda et al., 2019 (57) NCT02906930 31 Semaglutide Placebo 2/525 0/178 55.0 54.0 268 (51.0) 89 (50.0) 31.7 32.2 3
O’Neil et al., 2018 (58) NCT02453711 59 Semaglutide
Liraglutide
Placebo 0/718
0/103
1/136 46.3
49.0
46.0 254 (35.4)
36 (35.0)
48 (35.0) 30.0
30.4
30.7 3
Ahren et al., 2017 (59) NCT01930188 56 Semaglutide Sitagliptin 3/818 0/407 55.4 54.6 412 (50.3) 208
(51.1)
32.5 32.5 4
Aroda et al., 2017 (60) NCT02128932 36 Semaglutide Glargine 0/722 1/360 56.6 56.2 379 (52.5) 195 (54) 33.1 33.0 3
(Continued)
Hu et al. GLP-1RAs and Thyroid Disorders
Frontiers in Endocrinology | www.frontiersin.org July 2022 | Volume 13 | Article 9278595
interventions was 0.69 (95% CI 0.22‐2.20; Figure 3). There were
3 studies including 16220 patients that regarded exenatide as the
experimental agent, and the pooled RR of overall thyroid
disorders in patients receiving exenatide versus other
interventions was 0.82 (95% CI 0.21‐3.29; Figure 3). There
were 3 studies including 11633 patients that regarded
albiglutide as the experimental agent, and the pooled RR of
overall thyroid disorders in patients receiving albiglutide versus
other interventions was 0.76 (95% CI 0.31‐1.83; Figure 3). Most
of the above meta-analyses had no heterogeneity (I
2
= 0%), while
one had medium heterogeneity (I
2
= 33.1%).
TABLE 1 | Continued
Study Clinical Trial
Registration
Number
Trial Duration
(week)
Interventions Events/Patients (N) Age (years) Man (N, %) BMI (kg/m
2
) Jadad
score
Experimental Control Experimental Control Experimental Control Experimental Control Experimental Control
Marso et al., 2016
(17)
NCT01720446 109 Semaglutide Placebo 4/1648 6/1649 64.7 64.6 1013 (61.5) 989
(60.0)
––4
Gerstein et al., 2021
(61)
NCT03496298 126 Efpeglenatide Placebo 5/2717 0/1359 64.7 64.4 1792 (66.0) 940
(69.2)
32.9 32.4 5
OAD, oral antidiabetic drugs; IDegLira, insulin degludec/liraglutide; IGlarLixi, insulin glargine/lixisenatide Fixed Ratio Combination.
FIGURE 2 | Forest plot of GLP-1 receptor agonists versus comparators on
risk of overall thyroid disorders. GLP-1RAs, GLP-1 receptor agonists; RR, risk
ratios; CI, confidence interval.
FIGURE 3 | Forest plot of specific GLP-1 receptor agonists versus
comparators on risk of overall thyroid disorders. GLP-1RAs, GLP-1 receptor
agonists; RR, risk ratios; CI, confidence interval.
Hu et al. GLP-1RAs and Thyroid Disorders
Frontiers in Endocrinology | www.frontiersin.org July 2022 | Volume 13 | Article 9278596
Subgroup Analyses and Meta-
Regression Analyses
Subgroup analyses based on type of underlying diseases, type of
control, trial durations and pharmacokinetics. The results
showed that the type of underlying diseases, type of control,
trial durations and pharmacokinetics did not significantly affect
the effects of GLP-1 receptor agonists on overall thyroid
disorders (all P
subgroup
>0.05;Figure 4). The statistical
significance of the results from the meta-regression was
consistent with the subgroup analyses.
DISCUSSION
This meta-analysis is the first large sample study that was designed
to assess the relationship between the use of GLP-1 receptor
agonists and the occurrence of various thyroid disorders. As a
result, the following two major findings were produced. First,
compared with placebo or other interventions, GLP-1 receptor
agonists significantly increased the risk of overall thyroid disorders
by 28%. Second, among GLP-1 receptor agonists, only liraglutide
and dulaglutide showed increased trends in the risks of overall
thyroid disorders compared with placebo and other
antidiabetic drugs.
Despite the lack of consistent clinical and epidemiological
evidence, the potential link between GLP-1 receptor agonists and
thyroid cancer has received considerable attention. Rodent
studies have shown that treatment with liraglutide or once-
weekly exenatide is associated with thyroid C-cell proliferation
and the formation of thyroid C-cell tumors (11,63).
Therefore, the US Food and Drug Administration (FDA)
prohibits these therapies for patients with an individual or family
history of medullary thyroid carcinoma (MTC) or patients with
multiple endocrine neoplasia syndrome type 2 (MEN2).
However, these concerns are controversial in clinical trials. A
retrospective analysis of the FDA’s AERS database found that the
incidence of thyroid cancer treated with exenatide was 4.7 times
that of the control drug (14). Similarly, analysis of data from the
EudraVigilance database has found evidence from spontaneous
reports that GLP-1 analogues are related to thyroid cancer in
diabetic patients (64). However, a meta-analysis involving 25
studies showed that liraglutide had no significant correlation
with the increased risk of thyroid cancer (65). Although our
meta-analysis also showed that GLP-1 receptor agonists did not
increase the risk of thyroid cancer compared to placebo or other
interventions, in combination with previously available evidence,
patients at risk for thyroid cancer should be prescribed GLP-1
receptor agonists with caution.
To date, the potential mechanism of the unfavorable effects of
GLP-1 receptor agonists on thyroid disorders has not been
completely clear. The possible mechanisms are as follows. First, it
was reported that the mechanism of C-cell transformation in
rodents is by activation of the GLP-1 receptor on the C cell, and a
study has shown that GLP-1 receptor stimulation is a better
predictor of C-cell hyperplasia than plasma drug concentrations
of exenatide and liraglutide (66,67). Second, in addition to
medullary thyroid carcinoma and C-cell hyperplasia, the
expression of GLP-1 receptors in papillary thyroid carcinoma
(PTC) has been demonstrated. Gier et al. (68) reported positive
immunoreactivity for GLP-1 receptors in PTC tissues, detected
using a polyclonal anti-GLP-1 receptors antibody. Meanwhile, they
reported that GLP-1 receptors were expressed differently in non-
neoplastic thyroid tissues according to different inflammatory
states. GLP-1 receptors were expressed in normal thyroid tissues
with inflammation, but not in normal thyroid tissues without
inflammation. In addition, another study also confirmed the
expression of GLP-1 receptors in PTC and the expression rate of
GLP-1 receptors in PTC, which was almost 30% (69). Korner et al.
(70) ascertained the expression of GLP-1 receptors in various
human thyroid tissues by scintigraphy and demonstrated that few
normal thyroid tissueexpressed GLP-1 receptors. Therefore, GLP-1
receptors may be abnormally induced in cells derived from thyroid
follicles through inflammation, cell proliferation or tumorigenesis.
However, some of the mentioned studies used GLP-1 receptor
antibodies lacking specificity (71,72). Using another detection
method, Waser et al. found that neither normal nor hyperplastic
human thyroids containing parafollicular C cells express GLP-1
receptors (73). At present, the presence and importance of GLP-1
receptors in normal human thyroid remains controversial. Third,
GLP-1 might work through the phosphoinositol-3 kinase/AKT
serine/threonine kinase (PI3K/Akt) pathway and/or mitogen-
activated protein kinase/extracellular signal-regulated kinase
(MAPK/Erk) pathway. These two signaling pathways are also
critical in regulating cell growth and proliferation; accordingly,
they are closely related to cancer, including PTC. These two
signaling pathways are significant pathways for regulating cell
growth and proliferation, and thus they are closely related to
cancer formation (74). Finally, the GlP-1 receptor may be
associated with triiodothyronine (T3) levels. GLP-1 stimulates
type 3 iodothyronine deiodinase (D3) expression through the
GLP-1 receptor, and the regulation of intracellular (T3)
concentration by D3 may be involved in the stimulation of
FIGURE 4 | Subgroup analyses of the effects of GLP-1 receptor agonists on
the risk of overall thyroid disorders. P value calculated by c
2
statistics is shown.
Statistical significance of results from meta-regression was consistent.
Hu et al. GLP-1RAs and Thyroid Disorders
Frontiers in Endocrinology | www.frontiersin.org July 2022 | Volume 13 | Article 9278597
insulin secretion by GLP-1 (75). In addition, a clinical study showed
that exenatide treatment for 6 months significantly reduced the
serum TSH concentration in diabetic patients without thyroid
disease (76). In conclusion, some animal studies have provided
evidencethat the use of GLP-1 receptor agonists increases the risk of
thyroid disease, but this evidence has not been confirmed in
humans. Therefore, we performed this meta-analysis to clarify the
association of GLP-1 receptor agonists with thyroid disease in
clinical studies and preparation for future studies in humans.
Further prospective studies should be carried out to determine
the potential effects of GLP-1 receptor agonists on thyroid disease.
In the analysis of different types of GLP-1 receptor agonists,
we found that liraglutide and dulaglutide were significantly
associated with an increased risk of overall thyroid disorders.
However, individual tolerability and safety to GLP-1RA may
vary due to differences in molecular structures (77).
Furthermore, these different findings could explain with an
imbalanced sample size. It is worth noting that the significantly
increased risk of liraglutide is largely driven by the LEADER trial
(20) and that of dulaglutide is largely driven by the REWIND test
(42), both of which contributed more than 75% of the weight to
the overall results. Due to the lack of sufficient research, we
cannot draw a decisive conclusion until further research provides
more information. Among the included studies, only one was
related to short-acting exenatide (39), and two were long-acting
exenatide (18,40). Due to the small number of studies, we did
not separately analyze according to pharmacokinetics.
This review has two main strengths. First, this is the first
meta-analysis to comprehensively assess the risks of various
thyroid diseases associated with the use of GLP-1 receptor
agonists. Moreover, all included studies were RCTs. Second, no
or only mild heterogeneity was found in any of the meta-analyses
conducted in the present study.
We acknowledge that our study has several limitations. First,
almost every included study did not consider thyroid events as the
main result, only regarded them as safety results and did not
monitor the changes in thyroid function at the same time. In
addition, only trials reporting thyroid events were included in this
analysis, leading to an unclear risk of reporting bias. Second,
although this analysis included 45 studies with a fairly large
sample size, the low incidence of thyroid events resulted in a wide
confidence interval that reduced the certainty of our findings.
Moreover, the study groups considerably differ in size (52600 vs.
41463). Considering the slight difference in the rate of thyroid
disorders (0.39 vs. 0.31%), a significant influence on the primary
endpoint cannot be ruled out. The third limitation is that there may
be the potential for numerous indirect effects or confounding. For
example, reduction in BMI in obesity patients, caloric restriction,
and illness are all associated with different thyroid function test
(TFT) changes. Patients may be more stringently screened,
particularly for thyroid nodules/cancer in patients receiving GLP-
1 receptor agonists. Another limitation is that for thyroid cancer,
reporting specifically the cases of MTC vs. PTC would further the
goal of elucidating mechanisms of thyroid disease. However, we
found that some studies did not specify the type of thyroid cancer,
which would affect the accuracy of the results. Due to the lack of
standardization of adverse event reports and original data, we
cannot make comparisons according to different types. Finally,
although our meta-analysis showed that GLP-1 receptor agonists
increasedthe risk of overall thyroid disorder, due to the decrease in
sample size, it did not show statistically significant results for
specific thyroid disorder. Future large long-term RCTs with
primary or secondary outcomes, including thyroid disorders and
real-world data, are needed to elucidate the association between
GLP-1 receptor agonists and the risk of various thyroid disorders,
particularly thyroid cancer.
CONCLUSION
In conclusion, compared with placebo or other interventions,
GLP-1 receptor agonists did not increase or decrease the risk
of thyroid cancer, hyperthyroidism, hypothyroidism, thyroiditis,
thyroid mass and goiter. Due to the low incidence of various
thyroid disorders, these findings still need to be verified by
further studies.
DATA AVAILABILITY STATEMENT
The datasets presented in this study can be found in online
repositories. The names of the repository/repositories
and accession number(s) can be found in the article/
Supplementary Material.
AUTHOR CONTRIBUTIONS
JL and XL designed and outlined the work; WH, RS, RC, CL, RG,
WT, JZ and QZ drafted and revised the manuscript. Both authors
approved the final version of the article and agree to be
accountable for all aspects of the work. All authors contributed
to the article and approved the submitted version.
FUNDING
This work was supported in part by National Natural Science
Foundation of China (No. 82000799), Research Project
Supported by Shanxi Scholarship Council of China (No. 2020-
187), Scientific Research Project of Shanxi Provincial Health
Committee (No.2021068), The Doctoral Foundation of the
Second Hospital of Shanxi Medical University (No. 20200112)
and Natural Science Foundation of Shanxi Province
(No. 202103021224243).
SUPPLEMENTARY MATERIAL
The Supplementary Material for this article can be found online at:
https://www.frontiersin.org/articles/10.3389/fendo.2022.927859/
full#supplementary-material
Hu et al. GLP-1RAs and Thyroid Disorders
Frontiers in Endocrinology | www.frontiersin.org July 2022 | Volume 13 | Article 9278598
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