Fahrettin Kelestimur

Fahrettin Kelestimur
Yeditepe University · Endocrinology

Bachelor of Medicine

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345
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Publications

Publications (345)
Article
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Activation of the hypothalamic–pituitary–adrenal (HPA) axis using an insulin tolerance test (ITT) is a medical diagnostic procedure that is frequently used in humans to assess the HPA and growth-hormone (GH) axes. Whether sex differences exist in the response to ITT stress is unknown. Thus, investigations into the analysis of transcripts during act...
Article
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Purpose Our aim was to investigate the changes in the composition of oral and gut microbiota in patients with newly diagnosed acromegaly and their relationship with IGF-1 levels. Methods Oral and fecal samples were collected from patients with newly diagnosed acromegaly without comorbidities and from healthy controls. The composition of the microb...
Article
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Purpose To investigate the changes in peripapillary and subfoveal choroidal vascular indexes (CVI) before and after pituitary macroadenoma surgery by using a binarization method. Method In this cross-sectional study, we examined 17 eyes in 9 patients with pituitary macroadenomas who had undergone transsphenoidal pituitary surgery due to chiasmal c...
Article
SARS-CoV-2 may affect the hypothalamic-pituitary axis and pituitary dysfunction may occur. Therefore, we investigated neuroendocrine changes, in particular, secondary adrenal insufficiency, using a dynamic test and the role of autoimmunity in pituitary dysfunction in patients with COVID-19. The single-center, prospective, case-control study include...
Article
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A wide range of diseases result from environmental effects, and the levels of many native transcripts are altered. The alteration of non-coding RNAs (ncRNAs) and transmission of the variation to the next generation is increasingly recognized as a marker of disease. However, the determining signals and mechanisms of RNA-induced heritability remain u...
Article
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Purpose Glucagon stimulation test (GST) is used to assess the hypothalamo-pituitary-adrenal (HPA) and growth hormone (GH) axes with an incompletely defined mechanism. We aimed to assess if glucagon acted through fibroblast growth factor-21 (FGF-21) to stimulate cortisol and GH secretion. The secondary outcome was to determine the relationship of FG...
Chapter
Pituitary dysfunction has been reported to occur in 15% of patients following traumatic brain injury (TBI). High prevalence of pituitary dysfunction and its debilitating and potentially life-threatening effects that may be successfully treated made development of screening strategies essential. Many risk factors have been studied that would accurat...
Preprint
Traumatic brain injury (TBI) is one of the major health problems affecting millions of people worldwide leading to death or permanent damage. TBI affects the hypothalamic-pituitary-adrenal (HPA) axis either by primary injury to the hypothalamic-hypophyseal region or by secondary vascular damage, brain, and/or pituitary edema, vasospasm, and inflamm...
Article
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Background: The relationship between serum calcium (Ca) level to serum parathyroid hormone (PTH), phosphorus (P) levels and tissue properties of the parathyroid gland is unknown in primary hyperparathyroidism cases. Revealing this relationship may be useful for understanding the etiopathogenesis of primary hyperparathyroidism and determining the t...
Chapter
Congenital adrenal hyperplasia (CAH) is a group of disorders characterized by enzymatic defects in cortisol biosynthesis. Steroidogenic enzymes can mainly be divided into two groups: cytochrome P450 (CYP) and hydroxysteroid dehydrogenases/ketosteroid reductase (HSDs/KSR). The CYP enzyme group can metabolize more than one substrate and is involved i...
Preprint
Full-text available
Purpose: The SARS-CoV-2 may affect the hypothalamic-pituitary axis and pituitary dysfunction may occur. Therefore, we investigated neuroendocrine changes, particularly, secondary adrenal insufficiency using a dynamic test and the role of autoimmunity in pituitary dysfunction in the patients with COVID-19. Methods: The single-center, prospective, ca...
Article
The aim of the present study was to evaluate the sleep parameters of patients with Cushing syndrome (CS) at the time of diagnosis and 12-months after treatment. Thirty four newly diagnosed patients with endogenous CS (17 with ACTH-secreting pituitary adenoma, 17 with adrenal CS) and 23 controls with similar age were included in the study. Two polys...
Article
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Pregnancies are rare in women with pituitary adenomas, which may relate to hormone excess from secretory subtypes such as prolactinomas or corticotroph adenomas. Decreased fertility may also result from pituitary hormone deficiencies due to compression of the gland by large tumours and/or surgical or radiation treatment of the lesion. Counselling p...
Article
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PurposeMicrobiota has crucial biological importance for human well-being. Bidirectional interaction exists between microbiota and the host, and there have been no studies investigating this interaction in patients with acromegaly. We aimed to analyze the composition of microbiota in patients with newly diagnosed acromegaly.Method Stool samples were...
Article
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The hypothalamo-pituitary-adrenal (HPA) axis is one of the main components of the stress system. Maintenance of normal physiological events, which include stress responses to internal or external stimuli in the body, depends on appropriate HPA axis function. In the case of severe cortisol deficiency, especially when there is a triggering factor, th...
Article
Insulin has complex effects on cell growth, metabolism and differentiation, and these effects are mediated by a cell-surface bound receptor and eventually a cascade of intracellular signaling events. Among the several metabolic and growth-promoting effects of insulin, insulin resistance is defined as an attenuated effect of insulin on glucose metab...
Chapter
Traumatic brain injury (TBI), a growing public health problem worldwide, has recently been recognized as one of the leading causes of hypopituitarism. The main causes of TBI-induced pituitary dysfunction are car accidents, falls, violence, sports-related brain injury, and war accidents, including blast-related brain injuries. Car accidents and fall...
Article
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Introduction: It is well-known that pituitary dysfunction can develop as a result of traumatic brain injuries. One reason for such injuries is collision during contact sports. Objectives: The aim of this study was to investigate the effects of heading the ball and concussion on pituitary function in retired soccer players. Methods: Thirty-two reti...
Article
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The relationship between the endocrine system and autoimmunity has been recognized for a long time and one of the best examples of autoimmune endocrine disease is autoimmune hypophysitis. A better understanding of autoimmune mechanisms and radiological, biochemical, and immunological developments have given rise to the definition of new autoimmune...
Article
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Objective To investigate whether a combination of the low-dose (1 µg) adrenocorticotropin (ACTH) stimulation test and glucagon stimulation test (GST) could overcome the problem of equivocal results with the GST or ACTH test alone in patients with pituitary disorders. Subjects and methods The study included 41 adult patients with pituitary disorder...
Article
Objective We investigated newly diagnosed patients with endogenous CS for molecular changes in skin by biopsy before and a year after treatment of CS.Patients and methods26 Patients with CS and 23 healthy controls were included. All the patients were evaluated before and a year after treatment. Skin biopsies were obtained from abdominal region befo...
Article
Purpose: The study aimed to investigate whether repeat number in the androgen receptor (AR) gene has any contribution to phenotypes of the disease of androgen excess (polycystic ovary syndrome (PCOS), idiopathic hyperandrogenemia (IHA) and idiopathic hirsutism (IH) in a cohort of Turkish women. Methods: Three hundred and fifty-four voluntary pre...
Article
Introduction: Traumatic brain injuries (TBI) are reported to cause neuroendocrine impairment with a prevalence of 15% with confirmatory testing. Pituitary dysfunction (PD) may have detrimental effects on vital parameters as well as on body composition, cardiovascular functions, cognition, and quality of life. Therefore, much effort has been made to...
Article
Full-text available
Objective The insulin tolerance test (ITT) has been accepted as the gold standard test for assessing the integrity of the growth hormone (GH) – insulin-like growth factor (IGF-1) axis and the hypothalamic-pituitary-adrenal (HPA) axis. The goal of the test is to achieve clinical and biochemical hypoglycemia at a blood glucose level ≤ 40 mg/dL to eff...
Article
Objective The aim of the Acromegaly Consensus Group was to revise and update the consensus on diagnosis and treatment of acromegaly comorbidities last published in 2013. Participants The Consensus Group, convened by 11 Steering Committee members, consisted of 45 experts in the medical and surgical management of acromegaly. The authors received no...
Article
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Purpose After traumatic brain injury was accepted as an important etiologic factor of pituitary dysfunction (PD), awareness of risk of developing PD following sports-related traumatic brain injury (SR-TBI) has also increased. However there are not many studies investigating PD following SR-TBIs yet. We aimed to summarize the data reported so far an...
Article
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Introduction The prevalence of pituitary dysfunction is high following aneurysmal subarachnoid hemorrhage (aSAH) and when occurs it may contribute to residual symptoms of aSAH such as decreased cognition and quality of life. Hypopituitarism following aSAH may have non-specific, subtle symptoms and potentially serious consequences if remained undiag...
Article
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Purpose This review aimed to evaluate the data underlying the pathophysiology of TBI-induced hypothalamo-pituitary dysfunction. Methods Recent literature about the pathophysiology of TBI-induced hypothalamo-pituitary dysfunction reviewed. Results Traumatic brain injury (TBI) is a worldwide epidemic that frequently leads to death; TBI survivors te...
Article
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Introduction Hirsutism is a medical sign rather than a disease affects 5–8% of women of reproductive age. Hirsutism is associated with hyperandrogenemia in most patients excluding those with idiopathic hirsutism (IH). The most common cause of hirsutism is polycystic ovary syndrome (PCOS) followed by IH and idiopathic hyperandrogenemia (IHA); howeve...
Article
Traumatic brain injury is one of the major causes of disability and death particularly in young population. Recent clinical studies have demonstrated that traumatic brain injury induced pituitary dysfunction occurs more frequently than previously estimated and this may contribute to delayed diagnosis and treatment of hormonal abnormalities. Today,...
Article
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Introduction: Cushing's syndrome is a rare condition characterized by increased glucocorticoid levels. Dermatologically, it causes a variety of skin conditions such as atrophy, striae, acne, plethora, hypertrichosis, hirsutism, acanthosis nigricans, hyperpigmentation, alopecia, purpura and fragile skin. Although skin lesions of Cushing's syndrome...
Article
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Among various substances produced by C-cells, the most important one is calcitonin (CT) that is used for detection, postoperative follow-up and evaluation of individuals at risk of developing medullary thyroid carcinoma (MTC). However, the role of serum CT measurement in the evaluation of thyroid nodules has been widely discussed, and there is stil...
Article
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Introduction With the goal of generate uniform criteria among centers dealing with pituitary tumors and to enhance patient care, the Pituitary Society decided to generate criteria for developing Pituitary Tumors Centers of Excellence (PTCOE). Methods To develop that task, a group of ten experts served as a Task Force and through two years of iterat...
Article
The stimulability and supressibility of hypothalamo-pituitary–adrenal (HPA) axis and stimulability of growth hormone (GH) axis is not known in chronic insomnia (CI). We aimed to examine the effects of CI on HPA and GH axes by dynamic tests, and metabolic consequences. Eighteen CI patients and 14 controls, without any other accompanying sleep and me...
Article
Objective: Data regarding pregnancies in relation to pituitary tumors are limited. The effects of pregnancy on pituitary adenomas and the effects of adenoma itself (hormonal activity, mass effects and pituitary insufficiency) and/or treatment on the ongoing gestation and developing fetus were evaluated. Methods: The study was a retrospective stu...
Article
Background: Non-classic congenital hyperplasia (NCAH) due to 21-hydroxylase deficiency is a common autosomal recessive disorder characterized by androgen excess. Objective and rationale: We conducted a systematic review and critical assessment of the available evidence pertaining to the epidemiology, pathophysiology, diagnosis and management of...
Article
Buy Article Permissions and Reprints This special issue of Hormone and Metabolic Research presents the proceedings of the 4th international workshop (PDE 2015) on cyclic AMP (cAMP)/protein kinase A (PKA) signaling and phosphodiesterases (PDEs). The meeting took place at Erciyes University, in Kayseri, Turkey, ([Fig. 1]) and followed the previous wo...
Article
Growth hormone deficiency (GHD) can develop due to a variety of conditions, and may occur either as isolated or multiple pituitary hormone deficiencies. It has been previously demonstrated that GH is one of the most frequent hormonal deficiencies in adult patients with hypopituitarism. The most frequent classical causes of adult-onset GHD (AO-GHD)...
Article
Objective: Acne is not solely a cosmetic problem. The clinical importance of acne in the estimation of androgen excess disorders is controversial. Recently, the Amsterdam ESHRE/ASRM-sponsored third PCOS Consensus Workshop Group suggested that acne is not commonly associated with hyperandrogenemia and therefore should not be regarded as evidence of...
Chapter
Traumatic brain injury (TBI) is a crucially important public health problem around the world, which gives rise to increased mortality and is the leading cause of physical and psychological disability in young adults, in particular. Pituitary dysfunction due to TBI was first described 95 years ago. However, until recently, only a few papers have bee...
Article
Sheehan syndrome or postpartum hypopituitarism is a condition characterized by hypopituitarism due to necrosis of the pituitary gland. The initial insult is caused by massive postpartum haemorrhage (PPH), leading to impaired blood supply to the pituitary gland, which has become enlarged during pregnancy. Small sella turcica size, vasospasms (caused...
Article
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The purposes of the study were to compare serum total cortisol (STC), salivary cortisol (SaC) and calculated free cortisol (cFC) levels at baseline and after the adrenocorticotrophic hormone (ACTH) stimulation test in patients with severe sepsis (SS) and determine the suitability of use of SaC and cFC levels instead of STC for the diagnosis of adre...
Article
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Objective: Seamless transition of endocrine patients from the paediatric to adult setting is still suboptimal, especially in patients with complex disorders, i.e., Small for Gestational Age, Turner or Prader-Willi Syndromes; Childhood Cancer Survivors, and those with Childhood Onset Growth Hormone Deficiency. Methods: An Expert Panel meeting com...
Article
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Objectives The aim of this study was investigate effects of heading and concussion on pituitary dysfunction in soccer players. Methods 32 retired football players at the average age of 43.38 ± 5.49 (35 -59) who played professionally in Turkey Football League and 26 sedentary at the average age of 43.31 ± 6.38 (35 -59) were included in this study....
Article
Objectives: This study aims to determine the impact of severe sepsis (SS) on CD34⁺ cell counts in the peripheral blood and to compare these counts with those of healthy subjects. Patients and methods: CD34⁺ cell counts in the peripheral blood were measured in 20 patients with SS (12 males, 8 females; mean age 58.6±16.3 years; range 23 to 81 years)...
Article
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GH-secreting pituitary adenomas can be hypo-, iso- or hyper-intense on T2-weighted MRI sequences. We conducted the current multicenter study in a large population of patients with acromegaly to analyze the relationship between T2-weighted signal intensity on diagnostic MRI and hormonal and tumoral responses to somatostatin analogs (SSA) as primary...
Article
Hypophysitis is generally accepted as an autoimmune disease which is characterized by inflammation and cellular infiltration of the pituitary gland. It can be either primary or secondary. In this review, treatment of primary hypophysitis of various histological subtypes are discussed. Management of primary hypophysitis is usually symptomatic aiming...
Article
Several instances of RNA-mediated inheritance of phenotypic variation have been reported, among them metabolic disorders. We and others have observed that microinjection into naive fertilized mouse eggs of total sperm RNAs of obese and diabetic males maintained on high-fat diet induce the same pathological variation in the offspring. A role of nonc...
Article
Introduction: Traumatic brain injury (TBI) is a worldwide public health problem and has been recently documented as a cause of neuroendocrine dysfunction. It has been shown that hypopituitarism may develop nearly 10–20% of the TBI patients, and most common pituitary hormone deficiency after TBI is growth hormone deficiency (GHD). To date no study h...
Article
Introduction: Acromegaly is known to be associated with obstructive sleep apnea syndrome (OSAS) in about 60–70% of the cases. Both OSAS and acromegaly are thought to be responsible from cardiovascular diseases and endothelial dysfunction. The aim of the present study was to investigate the role of OSAS on cardiovascular effects of acromegaly. Mater...
Article
Introduction: Patients with Cushing’s Syndrome (CS) frequently have sleep complaints. The aim of the study was to evaluate the prevalance sleep disturbances and sleep structure of patients with CS. Materials and methods: 33 patients with CS were evaluated both clinically and with polysomnograhy (PSG) findings in terms of sleep disorders and data we...
Article
Full-text available
Background: Acne, stria and decreased skin elasticity are dermatological features of Cushing’s syndrome (CS). Although it is known that collagen mass in skin is decreased in CS and glucocorticoids play a role in acneiform skin lesions, the dermatological findings of CS has not previously been measured by reliable methods. Objective: The aim of the...
Article
Traumatic brain injury (TBI), a worldwide public health problem, has recently been recognized as a common cause of pituitary dysfunction. Circulating microRNAs (miRNAs) present in the sera are characteristically altered in many pathological conditions and have been used as diagnostic markers for specific diseases. It is with this goal that we plann...
Article
Full-text available
Hypophysitis is generally accepted as an autoimmune disease which is characterized by inflammation and cellular infiltration of the pituitary gland. It can be either primary or secondary. In this review, treatment of primary hypophysitis of various histological subtypes are discussed. Management of primary hypophysitis is usually symptomatic aiming...
Article
Full-text available
Thyrotropinomas are rare pituitary tumors that are difficult to diagnose due to their variety of clinical presentations. We describe three patients with thyrotropinoma and review the management of this disease based on current literature. Patient 1 had a typical acromegalic phenotype with a pituitary adenoma that secreted both growth hormone (GH) a...
Article
Purpose: Hypothyroidism has profound effects on multiple organs and systems including cellular oxidative damage. Thus, we aimed to investigate the effects of acute hypothyroidism on oxidative stress in patients with differentiated thyroid carcinoma (DTC). Patients: 33 patients with DTC were involved in the study. 23 healthy subjects matched for age...
Article
Full-text available
Objective: There is an increase in the incidence of cancer, and consequently in mortality rates, both in the world and in Turkey. The increase in the incidence and mortality rate of cancer are more prominent in our country as well as in other developing countries. The aim of this workshop was to determine the current status on prevention, screenin...
Article
Aim: To determine the impact of traumatic brain injury (TBI) and chest trauma (CT) on the number of peripheral blood (PB) stem cells in affected patients in comparison to normal controls. Additionally, the aim was to determine the relationship between CD34+ cell counts and TBI-induced hypothalamus-pituitary-adrenal axis dysfunction in the acute ph...
Article
Full-text available
The aim of this study was to evaluate and compare the effects of spironolactone and spironolactone plus metformin treatments on body mass index (BMI), hirsutism score, hormone levels, and insulin resistance in women with polycystic ovary syndrome (PCOS). Thirty-seven patients with PCOS were randomly assigned to receive spironolactone 100 mg/d (spir...
Article
Full-text available
Pituicytomas are very rare and benign primary tumors of the neurohypophysis or infundibulum. They originate from pituicytes and the clinical features vary depending on the location of the tumor. Immunohistochemistry has an important role in the diagnosis. There is no pathognomonic feature for pre-operative diagnosis. Diagnosis is generally establis...
Article
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Sheehan's syndrome (SS) is a parturition-related pituitary disease resulting from severe postpartum hemorrhage and can present with varying degrees of pituitary insufficiency. Pathological and clinical findings of SS were first described by Harold L. Sheehan in the previous century. Although his definitions are still valid, various studies and repo...
Article
Full-text available
Traumatic brain injury (TBI) is a well recognized public health problem worldwide. TBI has previously been considered as a rare cause of hypopituitarism, but an increased prevalence of neuroendocrine dysfunction in patients with TBI has been reported during the last 15 years in most of the retrospective and prospective studies. Based on data in the...