Variation Of TSH Research Articles

Interpretation of TSH results can be improved by reference values fluctuating in time.

The secretion of thyroid stimulating hormone (thyrotropin, TSH), is characterized by a marked circadian rhythm. Plasma or serum TSH values are significantly lower in the afternoon and in the evening as compared to the early morning. As in clinical practice, blood sampling time shows an important variation, a reliable assessment of thyroid status is often not an easy task for the clinician. The biological variation of TSH plays a major role in the intra-individual variability of TSH results in serum or plasma. The observed intra-day variation largely exceeds the reported inter-vendor variation and the coefficient of variation of clinical TSH assays. Therefore, a mathematical solution was sought for correcting interpretation of TSH results for sampling time. We have developed a cosinor model which allows to compensate TSH decision values for the fluctuating serum or plasma TSH concentrations throughout the day. The following mathematical function could be derived: corrected TSH cutoff_value (mIU/L)=0.40+0.24*cos(((π/12) *T)+6) in which T represents the time (hours). This mathematical function can be easily implemented into a laboratory's informatics system and furthermore allows a better tailored diagnosis of (subclinical) hyperthyroidism, regardless the blood sampling time. Implementing the corrected cut-off values result in a marked reduction of apparent (false positive) hyperthyroidism diagnosis, in particular in the afternoon.

ASSOCIATION OF EUTHYROID TYPE 2 DIABETES MELLITUS WITH HEMOGLOBIN AND SERUM BILIRUBIN LEVELS RELATING TO GLYCEMIC CONTROL - A RETROSPECTIVE STUDY

Background: Diabetes, along with its comorbidities, may increase the risk of anaemia by lowering iron absorption. In diabetic patients, thyroid illness was 14.7% prevalent. In 13% of T2DM patients, subclinical hypothyroidism was the most common thyroid condition. Diabetes glucose metabolism may be impacted by thyroid dysfunction, and variations in blood TSH have been linked to variations in glycatedhaemoglobin. Methodology: Retrospective study analysis of euthyroid type 2 diabetic patients who had attended the OPD in the department of General Medicine. The hospital records (case history from MRD) were used as the sources of information by following proper procedure in obtaining the same. Collection of data for a period of four years with Type 2 diabetes (FBS>126) and who did not possess any obvious clinical manifestations of thyroid disease was included for the study group. Results: PBS, HbA1C, LDL, TSH are highly significant with Fasting blood sugar with(p=0.00). FBS, RBC are highly significant with HbA1C (p=0.00). Uric acid, cholesterol,directbilirubin,haemoglobinishighlysignificantwithbilirubin(p=0.00).whereascholesterol, total billirubin are highly significant with haemoglobin (p=0.00). Hb showedpositive association with FT4. TAG, VLDL, Globulin showed negative association with FBS.HbisnegativelyassociatedwithTotalbilirubin.Cholesterolexhibitsstrongnegativeassociation with Hemoglobin (HbA1c ≥7). TSHwere associated with FBS. Direct bilirubinexhibits positive association with FBS and TotalCholesterol(HbA1c ≤7). Conclusion: Our study results outcome could be concluded that the thyroid status, haemoglobinandCBCcouldbeusefultoolforT2DMpatients.

The role of thyroid function in borderline personality disorder and schizophrenia: a Mendelian Randomisation study

BackgroundGenome-wide association studies have reported a genetic overlap between borderline personality disorder (BPD) and schizophrenia (SCZ). Epidemiologically, the direction and causality of the association between thyroid function and risk of BPD and SCZ are unclear. We aim to test whether genetically predicted variations in TSH and FT4 levels or hypothyroidism are associated with the risk of BPD and SCZ.MethodsWe employed Mendelian Randomisation (MR) analyses using genetic instruments associated with TSH and FT4 levels as well as hypothyroidism to examine the effects of genetically predicted thyroid function on BPD and SCZ risk. Bidirectional MR analyses were employed to investigate a potential reverse causal association.ResultsGenetically predicted higher FT4 was not associated with the risk of BPD (OR: 1.18; P = 0.60, IVW) or the risk of SCZ (OR: 0.93; P = 0.19, IVW). Genetically predicted higher TSH was not associated with the risk of BPD (OR: 1.11; P = 0.51, IVW) or SCZ (OR: 0.98, P = 0.55, IVW). Genetically predicted hypothyroidism was not associated with BPD or SCZ. We found no evidence for a reverse causal effect between BPD or SCZ on thyroid function.ConclusionsWe report evidence for a null association between genetically predicted FT4, TSH or hypothyroidism with BPD or SCZ risk. There was no evidence for reverse causality.

Multi-trait analysis characterizes the genetics of thyroid function and identifies causal associations with clinical implications

To date only a fraction of the genetic footprint of thyroid function has been clarified. We report a genome-wide association study meta-analysis of thyroid function in up to 271,040 individuals of European ancestry, including reference range thyrotropin (TSH), free thyroxine (FT4), free and total triiodothyronine (T3), proxies for metabolism (T3/FT4 ratio) as well as dichotomized high and low TSH levels. We revealed 259 independent significant associations for TSH (61% novel), 85 for FT4 (67% novel), and 62 novel signals for the T3 related traits. The loci explained 14.1%, 6.0%, 9.5% and 1.1% of the total variation in TSH, FT4, total T3 and free T3 concentrations, respectively. Genetic correlations indicate that TSH associated loci reflect the thyroid function determined by free T3, whereas the FT4 associations represent the thyroid hormone metabolism. Polygenic risk score and Mendelian randomization analyses showed the effects of genetically determined variation in thyroid function on various clinical outcomes, including cardiovascular risk factors and diseases, autoimmune diseases, and cancer. In conclusion, our results improve the understanding of thyroid hormone physiology and highlight the pleiotropic effects of thyroid function on various diseases.

RARE ASSOCIATION BETWEEN HASHITOXICOSIS, BASEDOW DISEASE AND PAPILLARY THYROID CARCINOMA.

We present the case of a 32 yeas old male, diagnosed 7 years ago with Graves disease, with numerous recidives which needed anti-thyroid medication, with poor response (hypo to hyper-thyroid status, with high variations of TSH and FT4) whom after a period of remission (8 months, no treatment) came in for a polymorphic symptomatology sugestive for hyperthyroidism. The hyperthyroid state was confirmed he had high TRAb (31 UI/ml vs. <1.75 UI/ml) - on his last check in the detection rate of TRAb was under 0.3 UI/ml. The thyroid ultrasound revels on the left lobe a small mass of 0.8/0.8 cm, with EU-TIRADS score of 4, that was newly diagnosed. Postoperative histopathology revealed papillary microcarcinoma developed on Hashitoxicosis- pT1aN0, of 1 mm in the middle of left thyroid lobe. The particularity of this case consists in a long evolution of Graves disease with numerous relapses, the appearance of a thyroid nodule after 7 years in which they identified a papillary microcacinoma associated with Hashimoto thyroiditis and also the postoperative recovery that was slowed by the parathyreoprive tetany.

Biological variation of serum thyrotropin and thyroid hormones concentrations determined at 8-week intervals for 1 year in clinically healthy cats.

Cats commonly develop thyroid disease but little is known about the long-term biological variability of serum thyroid hormone and thyrotropin (thyroid-stimulating hormone; TSH) concentrations. We aimed to determine the long-term biological variation of thyroid hormones and TSH in clinically healthy cats. A prospective, observational study was carried out. Serum samples for analysis of total thyroxine (T4, by radioimmunoassay [RIA] and homogenous enzyme immunoassay [EIA]), triiodothyronine (T3 ), free T4 (by dialysis), and TSH were obtained every 8 weeks for 1 year from 15 healthy cats, then frozen until single-batch analysis. Coefficients of variation (CV) within individual cats ( ) and among individual cats ( ), as well as the variation between duplicates (ie, analytical variation [ ]) were determined with restricted maximum likelihood estimation. The indices of individuality (IoI) and reference change values (RCVs) for each hormone were calculated. Some thyroid hormones showed similar (total T4 by EIA) or greater (TSH) interindividual relative to intraindividual variation resulting in intermediate to high IoI, consistent with previous studies evaluating the biological variation of these hormones weekly for 5-6 weeks. By contrast, total T4 (by RIA) and free T4 had a low IoI. Total T3 had a high ratio of to ; therefore, interindividual variation could not be distinguished from analytical variation. No seasonal variability in the hormones could be demonstrated. Clinicians might improve the diagnosis of feline thyroid disease by establishing baseline concentrations for analytes with intermediate-high IoI (total T4, TSH) for individual cats and applying RCVs to subsequent measurements.

Thyroid parameters variations in healthcare workers and students exposed to low-dose ionizing radiations

Background. Ionizing Radiations (IR) are an important occupational risk factor for the potential damage that can cause to workers' health and for their presence in numerous professional settings. Health care workers (HCW) can be exposed to IR from various sources, in particular from x-rays using radiological equipment, and represent the largest group of workers occupationally at risk, despite increased regulation and protection which caused exposure to low dose radiations. The thyroid gland is one of the most sensitive organs to damage and an important target of IR, leading to functional and organic diseases. The aim of this study is to assess the variations in thyroid hormones, in a population of HCW exposed to low-dose IR. Methods. 121 individuals of the Teaching Hospital Policlinico Umberto I in Rome exposed to low-dose of IR (78 HCW, 17 Residents and 26 Radiology Technicians Students) were observed assessing serum levels of different thyroid function parameters as free triiodothyronine, free thyroxine and thyroid stimulating hormone at T1, T2 and DeltaT. Age, gender, history of thyroid diseases, BMI and smoke were analyzed as possible influencing factors using linear and multiple logistic regression analysis. Results. Analyzing TSH, fT3 and fT4 serum levels, in two different measurement (T1 and T2) and considering Delta between them, adjusting for different confounding factors, data showed no variation of TSH levels related to occupational exposure, a decrease of fT3 hormone values in HCW and residents, and an increase of fT4 in HCW. Discussion. The analysis of our results revealed that hospital occupation has an impact on thyroid hormones variations, with an increase of fT4 and a decrease of fT3 and no variations of TSH. These results are in conflict with previous studies evidences, in which both free hormones decreased with a concomitant increase of TSH. Conclusion. Exposure to low dose IR influences levels of free thyroid hormones, with no variation in TSH, which could result in a functional or organic disease. For this reason it is recommended continuous surveillance through a periodic check of all the thyroid hormones for an overall view of each HCW. However, further studies are necessary to confirm hormones trend and assess any related thyroid diseases.

Relationship between Maternal Serum Thyroid-Stimulating Hormone and in vitro Fertilisation-Conceived Pregnancy Outcomes.

ABSTRACTBackground:Thyroid dysfunction impairs female fertility and pregnancy outcome. Optimal preconception and gestational TSH level is still debatable in IVF-conceived pregnancies.Aims:To explore the relationships of IVF success and pregnancy outcomes with maternal serum levels of TSH (at both preconception and 12-week IVF-conceived pregnancy). Also, to confirm or refute the recommended TSH level ≤2.5μIU/mL.Study Setting and Design:Retrospective cohort.Material and Methods:158 IVF-conceived pregnant women and 117 age-matched controls non-pregnant (≤39years, BMI 18.5-38kg/m2) were recruited. Preconception and 12-week IVF-conceived pregnancy serum samples were analysed for reproductive hormones, fasting glucose, insulin and TSH levels. Data of pregnant women at 28 weeks for GDM screening (75-gram OGTT) and up until delivery were included.Statistical Analysis:Binary logistic regression used to predict association between preconception TSH levels and IVF success, and pregnancy outcomes. Association of delta change of hormones was determined with linear regression. Significance level P≤0.05 with 95% confidence interval (CI).Results:Overall, median (IQR) age was 32(6)years, BMI 25.4(6.9)kg/m2, HbA1c 5.2(0.52)% and TSH 1.82(1.4)μIU/mL. There was no significant association between preconception TSH level and IVF success rate. During the first trimester of IVF-conceived pregnancy, delta change in TSH level was associated with that of progesterone (P=0.03). 12-week gestation TSH level did not predict adverse pregnancy outcomes (i.e. onset of GDM, delivery type and premature delivery); but a higher TSH level predicted earlier delivery in weeks. There was a higher risk of delivery by caesarean section when TSH>2.5μIU/mL.Conclusion:Variation of maternal TSH within normal range (0.4-4.0μIU/mL) at preconception and 12-week gestation has no predictive effect on IVF success and pregnancy outcomes in IVF-pregnancy. Our data provide no support for a recommended preconception TSH level ≤2.5μIU/mL in IVF-conceived pregnancy, but rather promote a preconception TSH level within normal range.

TSH Variations in Chronic Heart Failure Outpatients: Clinical Correlates and Outcomes.

Hypothyroidism is a frequently observed comorbidity in patients with chronic heart failure (CHF), possibly giving rise to unfavorable outcomes. The aim of the study was to evaluate the impact of TSH changes over time on cardiac function and prognosis of outpatients with CHF. Patients underwent clinical, electrocardiographic, and echocardiographic evaluations at baseline and after 12 months. Moreover, blood chemistry tests were performed to evaluate renal function, cardiac biomarkers, fT3, fT4, and TSH levels. Based on TSH serum levels, patients were retrospectively classified into four categories: Group 1, patients with improved thyroid function at one-year follow up vs. baseline; Group 2, patients with stable and mildly high TSH values (3.74 - 10 mUI/L); Group 3, patients with worsening thyroid function; Euthyroid patients Group, TSH levels within the normal range of reference at baseline as well as at 12 months follow-up. We considered as end-points: one-year changes of laboratory and echocardiographic parameters; hospitalizations due to worsening of HF (acute decompensated heart failure - ADHF); death for all causes. Among 257 patients, 174 (67.7%) were euthyroid at baseline and after 12 months. Group 1 patients (n. 22, 8.6%) showed a significant improvement in systolic and diastolic function, filling pressures, NT-proBNP and Galectin-3. Group 2 patients (n. 34, 13.2%) did not exhibit significant modifications in studied parameters. Group 3 patients (n. 27, 10.5%) showed worsening of diastolic function and NT-proBNP and a greater risk of ADHF (HR: 2.12; 95%CI: 1.20-3.74; p: 0.009) and death (HR: 4.05; 95%CI: 2.01-8.15; p<0.001). In patients with CHF, changes in thyroid function over time influenced echocardiographic parameters and biomarkers reflecting modifications of cardiac function and prognosis, thus suggesting the clinical relevance of thyroid deficiency screening and correction.

Method-dependent variation in TSH and FT4 reference intervals in pregnancy: A systematic review.

Gestational TSH and FT4 reference intervals may differ according to assay method, but the extent of variation is unclear and has not been systematically evaluated. We conducted a systematic review of published studies on TSH and FT4 reference intervals in pregnancy. Our aim was to quantify method-related differences in gestation reference intervals, across four commonly used assay methods, Abbott, Beckman, Roche and Siemens. We searched the literature for relevant studies, published between January 2000 and December 2020, in healthy pregnant women without thyroid antibodies or disease. For each study, we extracted trimester-specific reference intervals (2.5-97.5 percentiles) for TSH and FT4 as well as the manufacturer-provided reference interval for the corresponding non-pregnant population. TSH reference intervals showed a wide range of study-to-study differences with upper limits ranging from 2.33 to 8.30 mU/L. FT4 lower limits ranged from 4.40 to 13.93 pmol/L, with consistently lower reference intervals observed with the Beckman method. Differences between non-pregnant and first trimester reference intervals were highly variable, and for most studies, the TSH upper limit in the first trimester could not be predicted or extrapolated from non-pregnant values. Our study confirms significant intra- and intermethod disparities in gestational thyroid hormone reference intervals. The relationship between pregnant and non-pregnant values is inconsistent and does not support the existing practice in many laboratories of extrapolating gestation references from non-pregnant values. Laboratories should invest in deriving method-specific gestation reference intervals for their population.

Thyroid Function and Mood Disorders: A Mendelian Randomization Study.

BackgroundObservational studies suggest that even minor variations in thyroid function are associated with the risk of mood disorders, including major depressive disorder (MDD) and bipolar disorder (BD). However, it is unknown whether these associations are causal or not. We used a Mendelian Randomization (MR) approach to investigate causal effects of minor variations in TSH and FT4 levels on MDD and BD risk.MethodsWe performed two-sample MR analyses using data from the largest publicly available genome-wide association studies on normal-range TSH (N=54,288) and FT4 (N=49,269) levels, MDD (170,756 cases, 329,443 controls) and BD (20,352 cases, 31,358 controls). Secondary MR analyses investigated the effects of TSH and FT4 levels on specific MDD and BD subtypes. Reverse MR was also performed to assess the effects of MDD and BD on TSH and FT4 levels.ResultsThere were no associations between genetically predicted TSH and FT4 levels and MDD risk, nor MDD subtypes and minor depressive symptoms. A one standard deviation increase in FT4 levels was nominally associated with an 11% decrease in the overall BD risk (OR=0.89, 95%CI=0.80-0.98, P=0.022) and a 13% decrease in the BD type 1 risk (OR=0.87, 95%CI=0.75-1.00, P=0.047). In the reverse direction, genetic predisposition to MDD and BD was not associated with TSH nor FT4 levels.ConclusionsVariations in normal-range TSH and FT4 levels have no effects on the risk of MDD and its subtypes, and neither on minor depressive symptoms. This indicates that depressive symptoms should not be attributed to minor variations in thyroid function. Borderline associations with BD and BD type 1 risks suggest that further clinical studies should investigate the effect of thyroid hormone treatment in BD.

Thyroid Function During Pregnancy in A Multiethnic Population in Norway.

ContextEthnic differences in thyroid function during pregnancy have been reported. However, it is unclear if this is equally valid across ethnic groups within multiethnic populations.ObjectiveWe aimed to assess ethnic differences in thyrotropin (TSH) and free thyroxine (FT4), and the prevalence of thyroid dysfunction and thyroid autoimmunity during pregnancy.MethodsIn a population-based cohort of 785 pregnant women in Oslo, Norway, TSH, FT4, and thyroid peroxidase antibodies (TPO Abs) were measured twice: at gestational week (GW) 15 and 28, and urine iodine concentration at GW 15. Associations were assessed using multivariate linear regression.ResultsWe found ethnic differences in TSH levels at both time points, but not for fT4. South Asians had 0.42 mU/L (95% CI, 0.20-0.64) higher TSH than Europeans in GW 15. This difference persisted after adjusting for covariates (including TPO Ab positivity and iodine status), and increased further as pregnancy progressed. In contrast, East Asians had the lowest TSH. No new cases of overt hypothyroidism were detected in early pregnancy, but subclinical hypothyroidism was found in 6.6% among all, highest in South Asians (14.2%). Hyperthyroidism early in pregnancy was observed in 3.7% (almost all subclinical), highest in East Asians (11.9%). The prevalence of TPO Ab positivity was 4%, highest in South Asians (8%).ConclusionIn a multiethnic population of presumably healthy women, we found ethnic variations in TSH but not FT4 levels throughout pregnancy. South Asians had higher TSH and more subclinical hypothyroidism, not explained by their higher prevalence of TPO Ab positivity. Larger studies are needed to define ethnic- and trimester-specific reference ranges in pregnancy.

A prospective, observational clinical trial on the impact of COVID-19-related national lockdown on thyroid hormone in young males

Trying to manage the dramatic coronavirus disease 2019 (COVID-19) infection spread, many countries imposed national lockdown, radically changing the routinely life of humans worldwide. We hypothesized that both the pandemic per se and the consequent socio-psychological sequelae could constitute stressors for Italian population, potentially affecting the endocrine system. This study was designed to describe the effect of lockdown-related stress on the hypothalamic-pituitary-thyroid (HPT) axis in a cohort of young men. A prospective, observational clinical trial was carried out, including patients attending the male infertility outpatient clinic before and after the national lockdown for COVID-19 pandemic. The study provided a baseline visit performed before and a follow-up visit after the lockdown in 2020. During the follow-up visit, hormonal measurements, lifestyle habits and work management were recorded. Thirty-one male subjects were enrolled (mean age: 31.6 ± 6.0 years). TSH significantly decreased after lockdown (p = 0.015), whereas no significant changes were observed in the testosterone, luteinising hormone, follicle-stimulating hormone, estradiol and prolactin serum levels. No patient showed TSH serum levels above or below reference ranges, neither before nor after lockdown. Interestingly, TSH variation after lockdown was dependent on the working habit change during lockdown (p = 0.042). We described for the first time a TSH reduction after a stressful event in a prospective way, evaluating the HPT axis in the same population, before and after the national lockdown. This result reinforces the possible interconnection between psychological consequences of a stressful event and the endocrine regulation.

The method comparison and the verification of precision of Mindray CL-6000i thyroid function tests (TFTs)

Abstract Objectives Thyroid diseases are the most frequent endocrine disorders and thyroid function tests (TFTs) are the most commonly requested endocrine tests. The reliable measurements of these tests are quite important. The aim of our study was to determine the bias and to verify the precision of the newly introduced Mindray CL-6000i immunoassay system in the guidance of CLSI guidelines. Methods A precision and bias study was performed in Mindray CL-6000i analyzer for FT3, FT4, TSH, Anti-TG, and Anti-TPO tests by using BioRad quality control (QC) materials and serum samples, respectively. Bland–Altman difference plot and Passing-Bablok regression analysis was made for method comparison with Beckman Coulter DXI 800 analyzer. Results The repeatability coefficient of variations (CVs) of FT3, FT4, TSH, Anti-TG, and Anti-TPO tests were ≤2.36, ≤1.66, ≤2.38, ≤3.48, and ≤3.31% while within laboratory CVs were ≤2.85, ≤4.61, ≤2.59, ≤3.78, and ≤3.60%, respectively. The mean differences between the two methods obtained from Bland–Altman analysis for FT3, FT4, TSH, Anti-TG, and Anti-TPO were defined to be −19%, 1.95%, −5.9%, −3.5%, and 7.3%, respectively. Conclusions Mindray CL-6000i had good precision in all tests, but the difference between the two methods in some tests shows that the harmonization and standardization of TFTs initiated globally is required.

Subclinical thyroid dysfunction in the first trimester of pregnancy: 'Disease' versus physiological (pulsatile) variation in TSH concentrations.

There is no universal consensus regarding cut-off points for TSH in pregnancy, so concentrations of 2.5 or 4.0mIU/L were suggested for first trimester (Endocrine Society [2012] and ATA [2017] guidelines, respectively). Yet, the impact of physiological variation in TSH secretion has not been assessed. We assessed baseline concentrations of free T4, free T3 and TSH at 30-minute intervals (between 7.00 and 9.00hours) in 110 healthy pregnant women, age 30.2±6.0years, 9.9±2.4weeks of gestation, and in 19 female controls, age 28.9±10.7. Mean TSH concentrations in pregnant women were 1.62±1.26 mIU/L and on average varied by 39.5% (dispersion between the highest and the lowest TSH), with no difference in TSH variation between pregnant women and controls. Taking into account the highest TSH out of five consecutive measurements, TSH >2.5mIU/L and TSH above 4.0mIU/L were found in 23 (20.9%) and 10 (9.1%) pregnant women, respectively. In contrast, when the lowest TSH value was considered, then concentrations of TSH >2.5mIU/L and >4.0mIU/L were found in 14 (12.7%) and 4 (3.6%) women, respectively. This discrepancy was even more pronounced in aTPO-negative subjects (21 [21.2%] vs 8 [8.1%] women, for TSH >2.5mIU/L, and six [6.06%] vs one [1.01%], for TSH >4.0 mIU/L). Furthermore, either six (5.4%) or 10 (9.1%) women had TSH concentrations below 0.1mIU/L. In a significant number of patients, diagnosis of subclinical thyroid dysfunction could be erroneously made not as a result of 'disease', but as a result of physiological variation in TSH concentrations.

SUN-420 Spontaneous Changes in TSH Levels After Thyroidectomy During Long-Term Follow-Up

Background. Spontaneous serum TSH variations during levothyroxine replacement therapy and multiple dose changes in athyreotic patients seem to be frequent in clinical practice. Aim. To describe the rate and extent of spontaneous serum TSH variations in patients after total thyroidectomy for differentiated thyroid cancer (DTC) in real-life practice, and the number of resulting levothyroxine (LT4) dose adjustments. Methods. Data of DTC patients were prospectively collected at a single referral center between January 2005 and May 2019. TSH and fT4 serum levels, LT4 dose and formulation, and concomitant medications were recorded at 1, 3, and 12 months after primary treatment (surgery ± radioiodine therapy), and then yearly; the data were retrospectively evaluated for this study. Visit at one month was used to tailor LT4 dose and was not considered into the data analysis. Patients with structural evidence of disease or during pregnancy were excluded. Results. Data of 2883 evaluations (472 patients) were collected; at baseline, the median age was 49.7 years, 73.5% were females. The LT4 formulation administered at baseline were tablets (84.9%), liquid solution (11.4%), or soft-gel capsule (3.7%). Overall, in 27.5% of clinical evaluation with unchanged levothyroxine dose (341/1243), there were meaningful spontaneous TSH variations (defined as delta TSH > 1.5 mcUI/ml) at yearly follow-up visit. It is clinically significant: in 6.6% of visits, overt thyrotoxicosis was recorded. Furthermore, the treating clinicians decided to change the LT4 dose in 37.1% of cases. These figures were not significantly higher in the first years, and a rate above 25% persist even after ten years of follow-up. The median maintenance dose needed was 1.61 (interquartile range [IQR] 1.41-1.92) mcg/Kg/day for tablets, 1.54 (IQR 1.39-1.79) mcg/Kg/day for liquid solution, and 1.46 (IQR 1.23-1.71) mcg/Kg/day for soft-gel capsules. After correction for daily dose, there was no difference in the rate of TSH variations > 1.5 mcUI/ml, or in the absolute value of median delta of TSH between the three formulations. In 20.1% of patients, the LT4 formulation was changed during the follow-up: it was more common in patients with a known gastroenteric disease (OR 1.76, p=0.03). Conclusions. TSH spontaneous variations and dose adjustments are very common in patients after total thyroidectomy, even during long-term follow-up: wide variations happen in more than 1/4 of all visits, and dose changes are needed in more than 1/3 of all evaluations. We were more inclined to change LT4 formulation in patients with known interference in LT4 absorption: however, no difference in TSH variations was recorded between users of three different formulations, even if soft-gel capsules seem to have a lower maintenance dose.

SAT-449 Factors Associated with Reduced Thyroid Hormones in Cushing Syndrome Patients Before and After Surgical Cure

Background: Hypercortisolemia adversely affects thyroid hormone secretion. We previously described the temporal pattern of thyroid function recovery in 23 patients (1). However, the factors leading to suppression and recovery of the hypothalamic-pituitary-thyroid (HPT) axis in Cushing’s syndrome (CS) are not fully understood. We performed two separate studies to investigate these factors. Methods: In study 1, we examined patients (pts, n=62) with CS who underwent curative surgery and recorded their serum morning and evening cortisol, ACTH, tumor volume and duration of symptoms and 24-hour urine free cortisol (UFC) at baseline and the morning serum free T4, TSH and T3 at six-month intervals after cure. Data were log-transformed and Pearson correlations were performed. Linear mixed models were used to study factors that predict recovery of thyroid function. In study 2, we examined the diurnal variation of TSH by performing hourly TSH measurement between 3—7 PM and 12—4 AM on a cohort of pts (n=45) before surgery. Wilcoxon Signed-Rank method was used for comparisons of mean TSH across time and Pearson correlations were performed on log-transformed data. P values <.05 were considered significant. Results: Study 1: In this larger cohort, we confirmed previous findings of suppressed or low normal fT4 and TSH values with active hypercortisolism, with normalization after cure that reflected changes in the T3:TSH, fT4:TSH and T3:fT4 ratios. There were inverse linear correlations between log10 UFC, serum AM and PM cortisol; and log10 TT3, fT4 and TSH before surgery. Independent negative prognosticators of circulating fT4 recovery included UFC greater than 1000mcg/day (nl: 3.5—45mcg/day), duration of symptoms of less than one year, and ACTH levels greater than 60pg/mL(nl: 5—45pg/mL) Study 2: The nocturnal (12 - 4AM) TSH surge was reduced, so that the difference in day and night TSH values was not statistically significant; this contrasts with the 30—50% nocturnal TSH increase above daytime values seen in healthy subjects. There was an inverse relationship between UFC and nocturnal TSH, daytime TSH and TBG values, but there was no direct relationship between UFC and percent changes in nocturnal TSH values. Conclusions: Our findings suggest that a deficit in TSH stimulation of the thyroid gland may explain the reduction in T3 and T4 levels. There is a dose-response relationship between various measures of hypercortisolemia and both thyroid hormones and the pattern of TSH secretion. Finally, the severity of hypercortisolism correlates with a longer time to recovery of the HPT axis in pts with CS after curative surgery. 1. Shekhar S et al. HPG and HPT Axes in Cushing Syndrome. J Endocr Soc, 3 S1, April May 2019

Effect of vitamin D supplementation on TSH levels in euthyroid subjects with autoimmune thyroiditis.

The impact of vitamin D supplementation on thyroid function is not clear and the relationship between hypovitaminosis D and autoimmune thyroiditis (ATD) incidence and evolution is still a matter of debate. The aim of this study was to retrospectively evaluate the impact of vitamin D supplementation on thyroid function in subjects with and without ATD. One hundred and ninety-eight euthyroid subjects, with diagnosis of "hypovitaminosis D" (<30 ng/mL) who had been taking supplementation therapy with cholecalciferol for different time periods, were included. They were divided in two groups according to the previous diagnosis of ATD: "ATD-neg" group including subjects without ATD [n = 103 (52%)]; "ATD-pos" group including subjects with a confirmed diagnosis of ATD [n = 95 (48%)]. For both groups, we considered TSH and 25 hydroxyvitamin D (25OHD) levels before (T0) and after (T1) cholecalciferol supplementation. We also considered the treatment duration and the monthly dose of cholecalciferol expressed as IU/month. In hypovitaminosis D subjects with ATD, TSH levels significantly decreased after therapy with cholecalciferol 100.000 IU/month [mean ± SD, TSH at T0: 2.67 ± 1.21 vs. TSH at T1: 2.28 ± 0.86, p = 0.028]. No significant TSH variation was observed in ATD-neg group, irrespective of treatment dose and duration. As expected, 25OHD levels significantly improved with all monthly doses and especially in the group receiving 100.000 IU/month. Cholecalciferol supplementation improved thyroid function in euthyroid ATD-pos subjects affected with severe hypovitaminosis D. In particular, a significant reduction in TSH levels was observed in subjects with very low baseline 25OHD levels, after taking high monthly doses of cholecalciferol.

Changes in TSH levels in athyreotic patients with differentiated thyroid cancer during levothyroxine therapy: influence on dose adjustments.

The aim of the study was to describe the spontaneous TSH level variations and levothyroxine dose adjustments in athyreotic patients with differentiated thyroid cancer (DTC) in real-life practice. Patients with DTC were retrospectively evaluated at a tertiary referral center between October 2006 and November 2013. Hormone measurements (TSH and FT4 serum levels), L-T4 prescription information (dose per kg per day) and other medications were recorded at 1month and 3, 12, 24, 36 and 48months after primary treatment (surgery ± radioiodine therapy). The cohort was composed of 452 patients; about 20% of patients with stable levothyroxine dose have clinically meaningful spontaneous TSH variations (defined as ΔTSH > 2mcUI/mL) at yearly follow-up visit. Furthermore, about 25% of athyreotic DTC patients with stable dose have a ΔTSH > 1.5mcUI/mL and about 40% a ΔTSH > 1mcUI/mL during each follow-up visit. We further investigated whether this TSH variation would lead to subsequent dose changes. About 19.9-37.7% of DTC patients on stable LT4 dose on the previous visit had their levothyroxine dose reduced, while 7.8-14.9% increased due to TSH variations. We further evaluated the decision to change the dose in relation with the age-specific TSH range. Up to 77.2% of patients had their dose adjusted due to TSH falling below the age-specific range. Spontaneous serum TSH variations determine levothyroxine replacement therapy in athyreotic patients with DTC, requiring multiple dose changes.

Ultrasound findings of hypothyroidism during pregnancy

Hypothyroidism is the most common gestational en­do­­crine disease. Globally, the most common cause for hy­po­thy­ro­idism is iodine deficiency. Other causes in­clude: genetic va­riations that are responsible for TSH variations, prior thyroidectomy or ablative ra­dio­io­dine therapy, whereas secondary (pituitary) and tertiary (hypothalamic) causes are rare. Most inter­na­tio­nal guidelines suggest targeted thyroid testing in pregnant women with risk factors for thyroid insuf­fi­ciency, such as living in iodine-replete areas.