Peripheral markers of thyroid function: the effect of T4 monotherapy vs T4/T3 combination therapy in hypothyroid subjects in a randomized crossover study

Endocrine Unit, Department of Medicine O Herlev University Hospital Herlev RingvejDK-2730, Herlev Denmark.
Endocrine Connections 03/2013; 2(1):55-60. DOI: 10.1530/EC-12-0064
Source: PubMed


A recent randomized controlled trial suggests that hypothyroid subjects may find levothyroxine (l-T4) and levotriiodothyronine combination therapy to be superior to l-T4 monotherapy in terms of quality of life, suggesting that the brain registered increased T3 availability during the combination therapy.
Peripheral tissue might also be stimulated during T4/T3 combination therapy compared with T4 monotherapy.
Serum levels of sex hormone-binding globulin (SHBG), pro-collagen-1-N-terminal peptide (PINP), and N-terminal pro-brain natriuretic peptide (NT-proBNP) (representing hepatocyte, osteoblast, and cardiomyocyte stimulation respectively) were measured in 26 hypothyroid subjects in a double-blind, randomized, crossover trial, which compared the replacement therapy with T4/T3 in combination (50 μg T4 was substituted with 20 μg T3) to T4 alone (once daily regimens). This was performed to obtain unaltered serum TSH levels during the trial and between the two treatment groups. Blood sampling was performed 24 h after the last intake of thyroid hormone medication.
TSH remained unaltered between the groups ((median) 0.83 vs 1.18 mU/l in T4/T3 combination and T4 monotherapy respectively; P=0.534). SHBG increased from (median) 75 nmol/l at baseline to 83 nmol/l in the T4/T3 group (P=0.015) but remained unaltered in the T4 group (67 nmol/l); thus, it was higher in the T4/T3 vs T4 group (P=0.041). PINP levels were higher in the T4/T3 therapy (48 vs 40 μg/l (P<0.001)). NT-proBNP did not differ between the groups.
T4/T3 combination therapy in hypothyroidism seems to have more metabolic effects than the T4 monotherapy.

Download full-text


Available from: Birte Nygaard, Jul 16, 2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: Impaired psychological well-being, depression or anxiety are observed in 5-10% of hypothyroid patients receiving levothyroxine, despite normal TSH levels. Such complaints might hypothetically be related to increased free T4 and decreased free T3 serum concentrations, which result in the abnormally low free T4:free T3 ratios observed in 30% of patients on levothyroxine. Evidence is mounting that levothyroxine monotherapy cannot assure a euthyroid state in all tissues simultaneously, and that normal serum TSH levels in patients receiving levothyroxine reflect pituitary euthyroidism alone. Levothyroxine plus liothyronine combination therapy is gaining in popularity; although the evidence suggests it is generally not superior to levothyroxine monotherapy, in some of the 14 published trials this combination was definitely preferred by patients and associated with improved metabolic profiles. Disappointing results with combination therapy could be related to use of inappropriate levothyroxine and liothyronine doses, resulting in abnormal serum free T4:free T3 ratios. Alternatively, its potential benefit might be confined to patients with specific genetic polymorphisms in thyroid hormone transporters and deiodinases that affect the intracellular levels of T3 available for binding to T3 receptors. Levothyroxine monotherapy remains the standard treatment for hypothyroidism. However, in selected patients, new guidelines suggest that experimental combination therapy might be considered.
    Nature Reviews Endocrinology 01/2014; 10(3). DOI:10.1038/nrendo.2013.258 · 13.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: At present, the drug of choice for the treatment of hypothyroidism is levothyroxine sodium, even though the thyroid gland secretes both thyroxine and 3',3,5-triiodothyronine; the latter is the more active of the two at the cellular level because of its higher affinity for the nuclear thyroid hormone receptors. To date, combined levothyroxine plus liothyronine treatment for hypothyroidism has been evaluated in 15 clinical trials in humans. In two studies, combined therapy seemed to have beneficial effects on mood, quality of life, and psychometric performance of patients, compared with levothyroxine alone; in some of these studies, the patients preferred levothyroxine plus liothyronine combinations. This preference should be balanced against the possibility of adverse events resulting from the addition of liothyronine to levothyroxine. Until clear advantages of levothyroxine plus liothyronine are demonstrated, the administration of levothyroxine alone should remain the treatment of choice for replacement therapy of hypothyroidism. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Best Practice & Research: Clinical Endocrinology & Metabolism 10/2014; 29(1). DOI:10.1016/j.beem.2014.10.004 · 4.60 Impact Factor