Refik Tanakol

Background: Vitamin D deficiency is a common global health problem and remains highly prevalent in Türkiye, where limited food fortification and heterogeneous clinical practices contribute to variability in testing and supplementation strategies. Aims: To provide Türkiye-specific best practice recommendations for defining clinically relevant serum 25-hydroxyvitamin D [25(OH)D] thresholds, identifying adult risk groups for targeted testing, and recommending evidence-based prevention, treatment, and monitoring approaches while minimizing under-treatment and inappropriate high-dose use. Methods: This national expert consensus document was developed by endocrinologists from across Türkiye using a structured, modified Delphi methodology. Draft statements informed by systematic literature reviews were rated via online surveys using a 9-point Likert scale, followed by two Delphi rounds and a face-to-face consensus meeting in İstanbul in October 2025. Results: Recommendations addressed sun exposure, laboratory assessment, screening, supplementation, treatment, and follow-up. Serum 25(OH)D <20 ng/mL was defined as deficiency and <12 ng/mL as severe deficiency, with a target range of 20–50 ng/mL. Routine population-wide screening was not recommended; instead, targeted testing in high-risk adults and symptom-driven biochemical evaluation were endorsed. Empiric supplementation was recommended for selected high-risk groups, with cholecalciferol as the preferred agent. Higher individualized doses were suggested in obesity or malabsorption, while loading regimens were reserved for specific clinical indications, such as severe deficiency or certain medical conditions that impair vitamin D metabolism. Reassessment of 25(OH)D at 8–12 weeks was recommended. Conclusion: These consensus-based recommendations provide a practical, context-specific framework for assessing, preventing, treating, and monitoring vitamin D deficiency in adults in Türkiye.

Context: The aims of the study are to compare characteristics of subacute thyroiditis (SAT) related to different etiologies, and to identify predictors of recurrence of SAT and incident hypothyroidism. Methods: This nationwide, multicenter, retrospective cohort study included 53 endocrinology centers in Turkey. The study participants were divided into either COVID-19–related SAT (Cov-SAT), SARS-CoV-2 vaccine–related SAT (Vac-SAT), or control SAT (Cont-SAT) groups. Results: Of the 811 patients, 258 (31.8%) were included in the Vac-SAT group, 98 (12.1%) in the Cov-SAT group, and 455 (56.1%) in the Cont-SAT group. No difference was found between the groups with regard to laboratory and imaging findings. SAT etiology was not an independent predictor of recurrence or hypothyroidism. In the entire cohort, steroid therapy requirement and younger age were statistically significant predictors for SAT recurrence. C-reactive protein measured during SAT onset, female sex, absence of antithyroid peroxidase (TPO) positivity, and absence of steroid therapy were statistically significant predictors of incident (early) hypothyroidism, irrespective of SAT etiology. On the other hand, probable predictors of established hypothyroidism differed from that of incident hypothyroidism. Conclusion: Since there is no difference in terms of follow-up parameters and outcomes, COVID-19– and SARS-CoV-2 vaccine–related SAT can be treated and followed up like classic SATs. Recurrence was determined by younger age and steroid therapy requirement. Steroid therapy independently predicts incident hypothyroidism that may sometimes be transient in overall SAT and is also associated with a lower risk of established hypothyroidism.

SUMMARY Dilated cardiomyopathy (DCM) is characterized by systolic dysfunction and is usually idiopathic. A rare cause of reversible DCM is hypocalcemia. Calcium plays a key role in myocardial contraction. Hypocalcemia can lead to a decrease in contraction, left ventricular systolic dysfunction, and heart failure with reduced ejection fraction (EF). Hypocalcemia-related reversible DCM reports are rare. Herein, we present two cases with heart failure caused by hypocalcemia developed due to hypoparathyroidism. The first case presented with severe heart failure and an [...] SUMMARY Dilated cardiomyopathy (DCM) is characterized by systolic dysfunction and is usually idiopathic. A rare cause of reversible DCM is hypocalcemia. Calcium plays a key role in myocardial contraction. Hypocalcemia can lead to a decrease in contraction, left ventricular systolic dysfunction, and heart failure with reduced ejection fraction (EF). Hypocalcemia-related reversible DCM reports are rare. Herein, we present two cases with heart failure caused by hypocalcemia developed due to hypoparathyroidism. The first case presented with severe heart failure and an

The aim of the the study is to compare the effects of cholecalciferol and calcitriol on bone mineral metabolism in women with vitamin D deficiency. Calcitriol was associated with a significant increase in bone mineral density at the lumbar spine in patients with low vitamin D levels.

High GH and IGF I levels increase tubular phosphate reabsorption in patients with acromegaly. We aimed to investigate the utility of serum phosphorus levels as an indicator for predicting chance of remission in acromegaly patients.

Introduction: Thyrotropin-secreting pituitary adenomas (TSHomas) are a rare cause of hyperthyroidism and represent n=1) or thyroidectomy (n=2) was performed as a definitive treatment for hyperthyroidism before the correct diagnosis of TSHoma. The diagnosis delayed for 3–11 years. Four of the patients secrete TSH alone, while three of them were mixed adenomas [TSH, growth hormone (GH) (n=1); TSH, GH and prolactin (n=1); TSH, prolactin (n=1)]. Five of the cases had macroadenoma invading sphenoid and/or cavernous sinuses, and two of them also showed compression on optic tractus, one patient had microadenoma. The primary therapeutic approach was transsphenoidal surgery. İmmunohistochemically, GH, prolactin and TSH positivity was evident in two patients and one also showed diffuse Pit1 positivity. One patient showed positivity, for TSH and prolactin and another showed focal immunostaining for GH and FSH. No remission was noted in four patients and medical therapy with somatostatin analogues (SSAs) and thereafter cabergoline were started. Radiotherapy was performed for one patient postoperatively. Hormonal control was achieved in all treated patients. Conclusion: The delayed diagnosis of TSHoma usually cause inappropriate treatment of hyperthyroidism. Transsphenoidal surgery should be the first line treatment. If remission is not achieved medical therapy with SSAs and cabergoline and also radiotherapy should be options.

Osteoporosis, osteosclerosis, and lytic bone lesions have been observed in patients with systemic mastocytosis (SM). We examined bone mineral density (BMD) biochemical turnover markers and serum tryptase levels in SM, which is considered a rare disease. Seventeen adult patients (5 females, 12 males; median age: 33 years, range: 20-64) with mastocytosis were included in this study. We investigated the value of quantitative ultrasound (QUS) of the calcaneus in the assessment of BMD in SM patients, as well as BMD of the lumbar spine (L1-L4), femoral neck, and distal radius using dual energy x-ray absorptiometry (DXA) and plasma tryptase levels, biochemical markers of bone turnover. At lumbar spine L1-L4, the femoral neck, and the distal radius or as calcaneus stiffness, 12 of 17 patients had T-scores of less than -1 at least at 1 site, reflecting osteopenia. Three of 17 patients had T-scores showing osteoporosis (T-score <-2.5). There was no relationship between DXA and bone lesion severity. We also found a significant positive correlation between tryptase levels and disease severity, as well as between disease severity and pyridinoline (p<0.01 by Spearman's test). DXA and calcaneal QUS may not be appropriate techniques to assess bone involvement in SM patients because of the effects of osteosclerosis. This study further shows that the osteoclastic marker pyridinoline is helpful in patients with severe disease activity and sclerotic bone lesions to show bone demineralization.

Langerhans cell histiocytosis (LCH) is a rare disease in which the most common endocrine manifestation is diabetes insipidus (DI). Data on anterior pituitary function in patients with LCH are limited. Thus, the present study investigated anterior pituitary function in LCH patients with DI via the evaluation of clinical and radiological findings at disease onset and during follow-up. The present study retrospectively evaluated nine patients with LCH (five males and four females). All diagnoses of LCH were made following histological and/or immunophenotypic analyses of tissue biopsies, bronchoalveolar lavage, or cerebrospinal fluid (CSF). Basal and, if necessary, dynamic pituitary function tests were used to assess anterior pituitary function, and magnetic resonance imaging (MRI) scans were used to image the pituitary. The LCH treatment modality was based on organ involvement. The mean age at onset of DI was 27.6 years (range 15–60 years). One patient (11 %) exhibited single organ involvement, while eight patients (89 %) displayed multisystem organ involvement. On admittance, one patient had hypogonadotropic hypogonadism, one patient exhibited panhypopituitarism [hypogonadotropic hypogonadism, central hypothyroidism, hypocortisolism, and growth hormone (GH) deficiency], and four patients (44 %) displayed hyperprolactinemia. The MRI data revealed infundibular enlargement in seven patients (78 %), a thalamic mass in one patient (11 %), and the absence of the bright spot in all patients. A single patient (11 %) showed a mass in the pons that had a partially empty sella. The patients were treated with radiation therapy (RT), chemotherapy (CT), or a combination of both (RT + CT) and were followed up for a median of 91.8 months (range 2–318 months). Seven patients were assessed during the follow-up period, of whom four patients (57.1 %) developed anterior pituitary hormone deficiency, three (43 %) were diagnosed with GH deficiency, and one (14 %) exhibited gonadotropin deficiency. The gonadotropin deficiency in the patient, which was diagnosed on admittance, was resolved during the follow-up period. DI persisted in all patients, and the conditions of the seven patients who have remained on follow-up are stable. In the present study, patients with LCH exhibited altered function in the anterior pituitary as well as the posterior pituitary, which may be due to the natural course of the disease or the effects of treatment. The present findings indicate that anterior pituitary function should be assessed in LCH patients on admittance and during follow-up, especially in LCH patients with multisystem organ involvement.

Enormous evidence suggests that vitamin D deficiency could be linked to several chronic diseases, including cardiovascular disease, diabetes, obesity, depression and cancer. The purpose of this study was to examine the prevalence of vitamin D deficiency and its correlates to test the hypothesis that vitamin D deficiency was common among adult Turkish population, particularly in women. The Turkish Diabetes, Hypertension, Obesity and Endocrine Disease Survey (TURDEP-II) Jan to June 2010 data were analyzed for vitamin D levels in adult participants (n=9560, mean (S.D.) age: 45.3 (15.4) years, 64% women). Serum 25(OH)D was inversely correlated with PTH (r=−0.122, P4, vitamin B12, folates, IGF1, IGFBP3 and eGFR. Vitamin D deficiency was defined as 25(OH)D concentrations ≤20 ng/ml (≤50 nmol/l). The overall prevalence rate of vitamin D deficiency was 93%, with the highest rate seen in younger (Z scores showed that male gender, increase in total cholesterol (39.3 mg/dl), HDL-cholesterol (12.3 mg/dl) and IGF1 levels (69.0 ng/ml) positively associated; but eGFR (18.6 ml/min) and PTH (22.7 pg/ml) levels inversely associated with vitamin D (≥20 ng/ml). In conclusion, vitamin D deficiency was common among adult Turkish population, particularly in child-bearing age women. Given that vitamin D deficiency is linked to important risk factors of leading cause of morbidity and mortality in Turkey, it is important that health professionals should be aware of this connection and health authorities arrange intervention strategies, such as vitamin D fortification of foods to correct vitamin D deficiency at the population level.