Serum FT4 Concentrations Research Articles

Partial sleep restriction modulates secretory activity of thyrotropic axis in healthy men

Sleep and endocrine function are known to be closely related, but studies on the effect of moderate sleep loss on endocrine axes are still sparse. We examined the influence of partial sleep restriction for 2days on the secretory activity of the thyrotropic axis. Fifteen healthy, normal-weight men were tested in a balanced, cross-over study. Serum concentrations of thyrotrophin (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) were monitored at 1-h intervals during a 15-h daytime period (08:00-23:00h) following two nights of restricted sleep (bedtime 02:45-07:00h) and two nights of regular sleep (bedtime 22:45-07:00h), respectively. Serum concentrations of fT3 (P<0.026) and fT4 (P=0.089) were higher after sleep restriction than regular sleep, with a subsequent blunting of TSH concentrations in the evening hours of the sleep restriction condition (P=0.008). These results indicate profound alterations in the secretory activity of the thyrotropic axis after 2days of sleep restriction to ~4h, suggesting that acute partial sleep loss impacts endocrine homeostasis, with potential consequences for health and wellbeing.

Cystic ovarian follicles and thyroid activity in the dairy cow

Thyroid activity affects the functionality of the reproductive axis and thyroid dysfunction has been associated with ovarian hyperstimulation syndrome and polycystic ovarian syndrome, in human medicine. This study investigates serum17-<beta> estradiol, progesterone, thyrotropic and thyroid hormone levels, in cyclic dairy cows on heat (Group H) and in dairy cows with ovarian follicular cysts (Group FC). Both 17-<beta> estradiol and progesterone serum concentrations were statistically higher in cystic than in cyclic cows (estradiol: 8.51±1.91 vs 6.32±1pg/mL) (progesterone: 0.49±0.17 vs 0.13±0.03ng/mL), whereas TSH and fT4 serum concentrations were statistically lower in cows with cystic ovarian follicles (COF), compared to cyclic ones (TSH: 2.48±1.31 vs 3.56±1.03ng/mL) (fT4: 5.86±1.69 vs 8.63±1.08). fT3 serum levels were similar, in both cystic and cyclic subjects (2.94±0.65 vs 3.02±0.9, respectively). Based on these results it was decided to examine the function of the thyrothropic axis of dairy cows in a similar manner to that conducted on humans. If severe hypothyroidism should be found, a hormone replacement therapy could be attempted in cystic cows refractory to “ordinary” therapies.

The Status of Thyroid Hormones in Iron Deficient Patients in Bangladesh

To determine the relation between iron deficiency and the status of thyroid hormones in iron deficient patients. This case control study was done in the Department of Biochemistry, Bangabandhu Sheikh Mujib Medical University (BSMMU), during July 2006 to the June, 2007. Iron deficiency patient was considered as case a healthy control subject was considered as control. A total of 80 subjects were selected for study from those who were attended in out patient department of the above mentioned hospital were enrolled in this study. The mean (±SD) age of case and control were 33.48±11.03 years and 35.40±12.30 years with the range of 16-60 years and 15-60 years respectively. Male female ratio was 1:1.6 in the whole study subjects. Hemoglobin concentration, serum ferritin concentration were significantly (p&lt;0.05) higher in control group but serum TSH level was significantly (p&lt;0.05) higher in case group, however, serum FT3 was almost similar between case and control groups. In iron deficient patients, serum ferritin had no significant negative correlation (r=-0212; p&gt;0.05) with serum TSH and no correlation with serum FT4 concentrations and serum FT3 concentration which were (r=0.055; p&gt;0.05) and (r=0.147; p&gt;0.05) respectively. In control subjects, serum ferritin revealed that there was significant negative correlation (r=-0.337; p&lt;0.05) serum TSH. However, serum ferritin with serum FT4 concentration and serum ferritin with serum FT3 level showed no statistically significant correlation which were (r=0.283; p&gt;0.05) and (r=0.145; p&gt;0.05) respectively. On the other hand, there were no significant (p&gt;0.05) correlation of hemoglobin concentration and serum ferritin with serum TSH, free T3 and free T4 concentrations both in case and control group. There were no significant (p&gt;0.05) difference among serum TSH, free T3 and free T4 concentrations between male and female in both groups. Serum TSH level was significantly (p&lt;0.05) higher in iron deficient patients and no significant negative correlation, serum ferritin level. DOI: http://dx.doi.org/10.3329/medtoday.v24i1.13941 Medicine TODAY Vol.24(1) 2012 pp.1-4

Thyroid Status in Patients with Low Serum Ferritin Level

Iron deficiency is the most important but preventable nutritional problem in Bangladesh. Thyroid peroxidase, an iron containing enzyme, is essential for initial two steps of thyroid hormone synthesis which is a component of tissue iron. Tissue iron diminishes early in the course of iron deficiency. So thyroid hormone level may be altered in iron deficient patients. This case-control study was carried out in the Department of Biochemistry, Bangabandhu Sheikh Mujib Medical University (BSMMU) from July 2006 to June 2007. This study was done to find out the changes of thyroid hormonal activity in iron deficiency.In this study 72 subjects were selected from the out-patient department of the hospital. Patients with low serum ferritin level &lt;12 mgm/L were selected as cases (n=36) and healthy persons with normal serum ferritin level were taken as controls. Serum ferritin, thyroid stimulating hormone (TSH), free thyroxine (FT4) and free triiodothyronine (FT3) were measured in all study subjects. Values were expressed as mean ± SD. Unpaired 't' test and Pearson's correlation test were performed to see the level of significance and p value &lt;0.05 was taken as significant. Serum ferritin level in cases and controls were 6.78±4.05 mgm/L and 79.04±28.08 mgm/L respectively which showed significant difference (P&lt;0.0001).Serum TSH concentration in cases and controls were 3.32±1.54 mIU/L and 1.89±0.86 mIU/L respectively. Serum FT4 concentration in cases and controls were 11.66±1.77 pmol/L and 13/10±1.36 pmol/L respectively and that of FT3 were 3.00±0.68 and 3.31±0.61 pmol/L respectively. All showed significant difference between groups.Serum ferritin and Serum TSH showed significant negative correlation in controls whereas in cases they showed negative correlation which was not statistically significant.Both serum FT4 and FT3 revealed positive correlation with serum ferritin but that too was not significant statistically.Though the study failed to show any significant positive correlation between serum ferritin and thyroid hormones, lower level of thyroid status in iron deficient patients suggest that it could be a reflection of disturbed activities of iron dependent enzymes such as thyroid peroxidase that impairs thyroid hormone synthesis. However, a large scale study is recommeded to establish the fact.This study showed that there was significant difference in thyroid hormonal status between iron deficient patients and normal healthy persons. Therefore it can be concluded that iron deficiency may impair normal thyroid hormone status. DOI: http://dx.doi.org/10.3329/bjmb.v5i1.13424 Bangladesh J Med Biochem 2012; 5(1): 5-11

Common genetic variation in CYP1B1 is associated with concentrations of T4, FT3 and FT4 in the sera of polycystic ovary syndrome patients

CYP1B1 encodes an estrogen enzyme that oxidizes 17β-estradiol to 4-hydroxyestradiol. The evidence demonstrates there may be a relationship between CYP1B1 and thyroid function. To date, no study has evaluated if genetic polymorphisms that regulate concentrations of serum FT3 and FT4 contribute to Polycyctic Ovary Syndrome (PCOS). To identify polymorphisms in the CYP1B1 locus associated with PCOS, we genotyped three common polymorphisms across the CYP1B1 locus in 226 patients. A test for association of common variants with susceptibility to PCOS was conducted in a large cohort of 609 subjects. The functional polymorphism CYP1B1 L432V (rs1056836) is associated with serum T4 (P = 0.003), serum FT3 (P < 0.001) and serum FT4 concentrations (P < 0.001). Our study provides the first evidence that genetic variants in CYP1B1 can be associated with serum T4, FT4 and FT3 levels in PCOS. These findings imply novel pathophysiological links between the CYP1B1 locus and thyroid function in PCOS.

Possible Evolution of Autoimmune Thyroiditis in Hypothyroidism: Role of Obesity

Objective: It is not known whether the presence of obesity is responsible for a more severe autoimmune thyroiditis and consequently for a higher prevalence of hypothyroidism. The present study was addressed to investigate this aspect in a cohort of subjects, all affected by autoimmune thyroiditis, with a wide range of Body mass index (BMI) in euthyroidism or subclinical hypothyroidism. Design: 311 subjects were enrolled : 160 of them underwent levothyroxine treatment, since they were affected by subclinical hypothyroidism, defined as having a TSH level higher than 4.0 µU/ml (Group 1); 151 subjects were affected by autoimmune thyroiditis, but they were euthyroid (TSH: 0.7- 3.0 µU/ml) (Group 2). Methods: Family and medical history were carefully evaluated in all patients and, in particular, metabolic and cardiovascular diseases were investigated. Serum concentrations of FT4, FT3, TSH, antithyroglobulin (Tg-Ab) and antithyroperoxidase antibodies (TPOAb) were measured in all patients. BMI was calculated and thyroid morphology was evaluated using a high-resolution 7.5-MHz linear transducer. Results: Obesity (BMI > 30.0) was present in 44.4% of patients (71/160) in Group 1, and only in 22.3% (29/151) of patients in group 2 (p<0.0001). A logistic model used to assess whether the need for levothyroxine therapy (dependent variable) is related to obesity (independent variables), suggested that this two parameters were significantly associated (p= 0.03). Conclusions: This study indicates that overweight and obesity increase the risk of autoimmune thyroiditis and subclinical hypothyroidism. It may be that higher production of adipokines characterizing obesity may involve the thyroid gland, thus favoring the development of autoimmune thyroiditis and subclinical hypothyroidism.

The acute myxedema after hyperthyroidism treated by radioactive iodine and its sequelae

This is a case report of a female patient who developed, after radioactive iodine therapy for Grave's hyperthyroidism, a severe clinically manifested hypothyroidism, which was accompanied by predominantly sensory neuropathy of dominant axonal type. Besides symptoms and neurophysiological signs of polyneuropathy, the patient, in spite of seemingly adequate levothyroxine monotherapy for hypothyroidism during the last 2 years, still manifested persistent hypothyroid symptoms by CNS, higher serum concentrations of total and LDL cholesterol and clinical signs of the increased peripheral vascular resistance. Non-physiological serum FT3 and FT4 ratio was maintained, together with serum TSH and FT4 concentrations, which suggested lower sensitivity of thyroid-hypophyseal negative feedback. The introduced combined LT4/LT3 substitution therapy resulted in quick subsidence of CNS-related hypothyroid symptoms, significant reduction of serum concentrations of total and LDL cholesterol, FT3/FT4 ratio normalization, at least in the first hours of drug administration, and disappearance of clinical signs of the increased peripheral vascular resistance. The extent of polyneuropathic difficulties was reduced to the level of not disturbing the sleep. Time and control ENG will show the final effects of combined T4/FT3 therapy on the peripheral nerve injuries. In the first 6 months, no adverse effects of this therapy were recorded.

Thyroid hormone concentrations differ between donkeys and horses

Reference intervals for thyroid hormones (TH) concentrations have not been previously established for donkeys, leading to potential misdiagnosis of thyroid disease. To determine the normal values of TH in healthy adult donkeys and compare them to TH values from healthy adult horses. Thirty-eight healthy Andalusian donkeys and 19 healthy Andalusian horses from 2 different farms were used. Donkeys were divided into 3 age groups: <5, 5-10 and >11 years and into 2 gender groups. Serum concentrations of fT3, tT3, rT3, fT4 and tT4 were quantified by radioimmunoassay. All blood samples were collected the same day in the morning. None of the animals had received any treatment for 30 days prior to sampling or had any history of disease. Both farms were in close proximity and under similar management. Differences between groups were determined using a one-way ANOVA analysis followed by Fisher's LSD test. P<0.05 was considered significant. Serum TH concentrations were higher in donkeys than in horses (P<0.01). Donkeys <5 years had higher serum rT3, fT4 and tT4 concentrations than donkeys >5 years (P<0.05). Furthermore, older donkeys (>11 years) had lower serum fT3 and tT3 concentrations than younger donkeys' groups (<5 and 5-10 years, P<0.05). TH concentrations were not different between genders (fT3: P = 0.06; tT3: P = 0.08; rT3: P = 0.15; fT4: P = 0.89; and tT4: P = 0.19). Thyroid hormone concentrations are different between healthy adult donkeys and horses. Establishing species-specific TH reference ranges is important when evaluating clinicopathologic data in equids in order to avoid the misdiagnosis of thyroid gland dysfunction. Further studies to elucidate the physiological mechanisms leading to these differences are warranted.

Smoking and Early Pregnancy Thyroid Hormone and Anti-Thyroid Antibody Levels in Euthyroid Mothers of the Northern Finland Birth Cohort 1986

Smokers in the general population have lower thyrotropin (TSH) and higher free triiodothyronine (fT3) and free thyroxine (fT4) concentrations, but the results in pregnant population vary from no effect to a decrease in TSH and fT4 concentrations and an increase in fT3 levels. Our objective was to further evaluate the question of whether there is an association between smoking, before and during pregnancy, with maternal thyroid function during pregnancy and with the risk for subsequent hypothyroidism. Our study population was a prospective population-based cohort (N=9362), the Northern Finland Birth Cohort 1986, with extensive data throughout gestation. The mothers underwent serum sampling in early pregnancy. The samples were assayed for TSH, fT3, fT4, thyroid-peroxidase antibodies (TPO-Ab), and thyroglobulin antibodies (TG-Abs) (n=5805). Mothers with thyroid dysfunction diagnosed before or during pregnancy were excluded, leaving 4837 euthyroid mothers. The smoking status of mothers and fathers were requested by questionnaires during pregnancy. Subsequent maternal morbidity relating to hypothyroidism 20 years after the index pregnancy was evaluated using national registers. Euthyroid mothers who smoked before, or continued smoking during first trimester of pregnancy, had higher serum fT3 (p<0.001) and lower fT4 (p=0.023) concentrations than nonsmokers. Smoking in the second trimester was associated with higher fT3 (p<0.001) concentrations, but no difference in fT4 concentrations compared with nonsmokers. TG-Abs were less common among smoking than nonsmoking mothers (2.5% vs. 4.7%, p<0.001), but the prevalence of TPO-Ab was similar. Paternal smoking had no independent effect on maternal early pregnancy thyroid hormone or antibody concentrations. The risk of subsequent maternal hypothyroidism after follow-up of 20 years was similar among prepregnancy smokers and nonsmokers. In euthyroid women, smoking during pregnancy was associated with higher fT3 levels and lower fT4 levels; possibly reflecting smoking-induced changes in peripheral metabolism of thyroid hormones. No differences were found in TSH concentrations between smokers and nonsmokers. Our results differ from those of the general population, which usually have shown smoking-induced thyroidal stimulation. This is possibly due to pregnancy-induced changes in thyroid function. Decreases in fT4 levels among smokers might predispose to hypothyroidism or hypothyroxinemia during pregnancy. Despite these changes in thyroid function, smoking did not increase the woman's risk of subsequent hypothyroidism.

Inverse Association Between Serum Free Thyroxine Levels and Hepatic Steatosis: Results from the Study of Health in Pomerania

Associations between thyroid function and hepatic steatosis defined by enzymatic and sonographic criteria are largely unknown in the general population. Thus, the aim of the present study was to investigate the association between thyroid function tests and sonographic as well as enzymatic criteria of liver status in a large population-based study, the Study of Health in Germany (SHIP). Data from 3661 SHIP participants without a self-reported history of thyroid or liver disease were analyzed. Hepatic steatosis was defined as the presence of a hyperechogenic ultrasound pattern of the liver and increased serum alanine transferase concentrations. Serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) concentrations were associated with hepatic steatosis using multinomial regression models adjusted for sex, age, physical activity, alcohol consumption, waist circumference, and food intake pattern. We detected no consistent association of serum TSH and FT3 concentrations with hepatic steatosis. In contrast, serum FT4 concentrations were inversely associated with hepatic steatosis in men (odds ratio (OR)=0.04 [95% confidence interval (CI)=0.01; 0.17]) and women (OR=0.06 [95% CI=0.01; 0.42]). Results from the present cross-sectional study suggest that low FT4 concentrations are associated with hepatic steatosis. Longitudinal and intervention studies are warranted to investigate whether hypothyroidism increases the risk of hepatic steatosis or vice versa.

Seasonal influence on the thyroid gland in healthy dogs of various breeds in different weights

The aim of our study was to evaluate the influence of seasonal ambient temperature on the thyroid gland function in terms of serum total thyroxine (TT4), free thyroxine (fT4), total triiodothyronine (TT3), and canine thyroid stimulating hormone (cTSH) concentrations in healthy dogs of various breeds living outdoors and to compare them with those living indoors in flats and houses. The monitoring was conducted for 5 years and our study included 162 indoor dogs and 148 outdoor dogs of both sexes from 2 to 12 years of age, categorised into 3 groups according to their body weight: large (n = 17), medium (n = 16) and small (n = 17) breeds. Comparison of the seasonal serum TT4 and fT4 concentrations in both the indoor and outdoor dogs confirmed their fluctuation in relation to the ambient temperature in all weight groups with the lowest average of TT4 and fT4 concentrations recorded in summer and the highest ones in winter. In dogs kept outdoors, the fluctuation of hormone values was significant (P&lt; 0.05). Seasonal serum cTSH fluctuation was found to be significant (P&lt; 0.05) only in the medium breeds living outdoors, but their concentrations did not exceed the reference ranges. The 5-year monitoring of serum TT3 in indoor and outdoor dogs of large, medium, and small breeds clearly showed that its concentrations were not influenced by varying ambient temperature. The study provides for the first time evidence that serum TT4 and fT4 concentrations in dogs kept outdoors directly depend on ambient temperature. This correlation was also expressed by mathematical equations.

Relationships between thyroid hormones and serum energy metabolites with different patterns of postpartum luteal activity in high-producing dairy cows

This study investigated the relationships of thyroid hormones, serum energy metabolites, reproductive parameters, milk yield and body condition score with the different patterns of postpartum luteal activity in the postpartum period. A total of 75 multiparous healthy (free of detectable reproductive disorders) Holstein dairy cows (mean peak milk yield = 56.5 ± 7.0 kg/day) were used in this study. Transrectal ultrasound scanning and blood sample collection were performed twice weekly. Serum concentrations of progesterone (P4) were measured twice weekly and beta-hydroxybutyrate (BHBA), non-esterified fatty acids, thyroxine (T4), 3,30,5-tri-iodothyronine (T3), free thyroxine (fT4) and free 3,30,5-tri-iodothyronine (fT3) were measured every 2 weeks from the 1st to the 8th week postpartum. On the basis of the serum P4 profile of the cows, 25 (33.4%) had normal luteal activity (NLA), whereas 30 (40%), 10 (13.3%), 6 (8%) and 4 (5.3%) had prolonged luteal phase (PLP), delayed first ovulation (DOV), anovulation (AOV) and short luteal phase, respectively. Serum T4 concentrations in PLP cows were higher than that in NLA cows at the 3rd week postpartum and did not change during the period of study, whereas in the NLA cows the concentrations increased (P < 0.05). Further, the least square (LS) mean of serum fT4 concentrations in the DOV and AOV cows were significantly lower than in the NLA cows during the study period (P < 0.05). In addition, the AOV cows had higher LS mean serum BHBA and T4 concentrations than the NLA cows in early weeks postpartum (P < 0.05). In conclusion, the serum thyroid hormones’ profile differs in high-producing dairy cows showing PLP, AOV and DOV in comparison with the postpartum NLA cows.

No association between affective and behavioral dysregulation and parameters of thyroid function in youths

Evidence from adults suggests that changes in thyroid function are associated with the development of bipolar disorder (BD) and severe mood dysregulation. A dysregulation profile based on the Child Behavior Checklist (CBCL-DP) describes a phenotype with severe mood problems in youth. The present study investigated whether altered thyroid functioning in youths is associated with the severe mood dysregulation symptoms characterized by the CBCL-DP. We analyzed the thyroid function data from 262 children and adolescents (n = 262 for serum TSH, n = 148 for free triiodothyronine [fT3] and n = 153 for free thyroxine [fT4]) with their CBCL-DP composite score. We created and compared high CBCL-DP and low CBCL-DP subgroups with regard to their serum TSH, fT3 and fT4 concentrations as well as the presence or absence of subclinical hypothyroidism. We did not detect between-group differences in serum TSH, fT3 and fT4 concentrations, nor were there significant correlations between youths' CBCL-DP scores and their serum TSH, fT3 and fT4 concentrations for either the whole sample or any subgroup. Post-hoc power analyses indicated that adequate to moderate power existed to detect between-group differences in fT3 and fT4 concentrations, respectively, but that larger TSH samples would be required to detect the same differences in those concentrations. This study had a retrospective design, fewer females than males, and reduced power with respect to TSH concentrations. The present investigation does not support the association between elevated serum-TSH concentrations and severe mood dysregulation in youths. However, these findings should be confirmed in future large-scale studies.

Real‐time ultrasound elastography in the diagnosis and differential diagnosis of subacute thyroiditis

To assess the value of real-time sonographic (US) elastography in the diagnosis of subacute thyroiditis (SAT). This study included 29 lesions from 20 patients with SAT, 33 nodules from 24 patients with multinodular goiter, and 27 nodules from 23 patients with thyroid cancer. Eighty-nine lesions in these patients were examined by grayscale US and real-time US elastography. An elasticity score (ES), based on four classes of tissue stiffness (class 1 for soft lesions; class 2 and 3 for lesions intermediate in stiffness; class 4 for inelastic lesions), was introduced. The distribution of ESs for SAT and multinodular goiter or thyroid cancer was compared. Also, the correlation between serum-free thyroxine (FT4) concentrations and ESs for lesions in patients with SAT was analyzed. Nineteen of 29 SAT lesions had an ES of 3; the rest had an ES of 4. Of 33 multinodular goiter nodules, 5 had an ES of 1, 23 had an ES of 2, and 5 had an ES of 3. Eleven of 27 malignant thyroid nodules had an ES of 3; 15 had an ES of 4, and 1 had an ES of 2. In the distribution of ESs, there was a statistically significant difference between SAT lesions and multinodular goiter nodules (p < 0.05), but there was no significant difference between SAT lesions and malignant nodules (p > 0.05). No correlation existed between serum FT4 concentrations and ESs for the lesions in patients with SAT (p > 0.05). Real-time US elastography does not provide conclusive information in the diagnosis and differential diagnosis of SAT due to its inability to distinguish between SAT and thyroid cancer.

Effect of dietary consumption of sheep meat on thyroid hormone levels and energy expenditure of Sprague - Dawley rats

The purpose of the present study was to investigate the effects of a sheep meat-based diet on the thyroid hormone concentrations and energy expenditure of Sprague–Dawley rats. The diets, a sheep meat diet (SMD) or a casein control diet (CD), each based on a standard formulation (AIN-93G), contained 18.3% protein, 7.4% fat and 60.0% carbohydrate, and were isocaloric (15.9kJ/g dry matter). Serum tri-iodothryonine (T3), thyroxine (T4), free tri-iodothyronine (FT3) and free thyroxine (FT4) concentrations, oxygen consumption rate (OCR), bodyweight, bodyweight gain and activities of liver sodium–potassium-adenosinetriphosphatase (Na,K-ATPase) and Ca2+-dependent adenosine triphosphatase (Ca-ATPase) were measured. Compared with the CD, the SMD increased the serum FT3 concentration on Day 7 (P = 0.004) and Day 14 (P &lt; 0.001). Serum albumin concentrations, which may influence the amount of thyroid hormones bound, were significantly lower in the SMD group on Day 7 (P &lt; 0.001) and Day 14 (P = 0.02) than those in the CD group. Both liver Na,K-ATPase and Ca-ATPase activities were significantly higher in rats consuming the SMD on Day 7 (P &lt; 0.001, P = 0.001) and Day 14 (P &lt; 0.001, P &lt; 0.001) respectively. OCRs were significantly higher in rats consuming the SMD on Day 6 (P = 0.023) and Day 13 (P = 0.014). Both bodyweight and bodyweight gains were significantly lower in the SMD group. We concluded that sheep meat consumption decreased the serum albumin concentrations, which increased the serum FT3 concentrations. This lead to FT3 promoting the OCRs and the activities of Na,K-ATPase and Ca-ATPase, resulting in reduced bodyweight and bodyweight gain, presumably through greater energy expenditure. Thus, energy expenditure appears to have been enhanced in rats fed the SMD.

Seasons but not ethnicity influence urinary iodine concentrations in Belgian adults

Mild iodine deficiency (MID) is endemic in Belgium. Previous surveys, which assessed iodine nutrition in Belgium, focused on children. The iodine status of adults and the influence of ethnicity or seasonality on urinary iodine concentrations (UIC) have not been investigated. Since the nutritional profile of children differs from that of adults, we may anticipate similar differences in iodine status. Seasonal fluctuations in UIC have also been reported from other MID regions. We aimed at assessing iodine status and its association with ethnicity and seasonality in adults. A stratified random sample of 401 healthy subjects aged between 40 and 60years, of Belgian, Moroccan, Turkish and Congolese descent residing in Brussels was obtained. Iodine status and thyroid function were determined. Median UIC was 68μg/L. The frequency of UIC below 100μg/L was 73.3%, of which 41.9% fell between 50 and 99μg/L, and 29.8% between 49 and 20μg/L. There was no difference in UIC and thyroid function between subjects of different ethnic origins. The frequency of UIC below 50μg/L was higher in the fall-winter compared to spring-summer periods (P=0.004). Serum FT3 concentrations, but not FT4 and TSH, were significantly greater in winter than in summer. Seasonal fluctuations in UIC suggest that the risk of iodine deficiency among adults living in Brussels is higher in fall-winter than in spring-summer. The prevalence of MID in Brussels is high among adults but ethnicity does not appear to influence iodine status.

Thyroid hormones profile in students of Makerere College of Health Sciences in Kampala Uganda

Serum concentrations of thyroxine (T4), triiodothyronine (T3) and Thyroid Stimulating Hormone (TSH) are used to assess thyroid function. It is recommended that each laboratory or hospital should establish its own reference values of T4, T3 and TSH for their clients because these hormones vary with ethnicity, geographical and climatic conditions of a population. There is no documented study which has been done to determine the Thyroid hormones profile in Ugandan general population. This study is one of the first attempts to determine Thyroid hormones profile in healthy Ugandans. The main objective of this study was to determine the thyroid hormones profile of students of the Makerere College of Health Sciences in Kampala, Uganda. A cross sectional descriptive study was done involving 72 students, with the mean age of 24.17 +/- 4.48 years. Subjects who volunteered to participate in the study were interviewed; their height and body weight measured, 5 ml of blood withdrawn, and sera harvested. FT4 and T3 Radioimmuno Assay (RIA) were done and TSH was assayed using Immunoradiometric Assay (IRMA) technique. The mean serum concentration of FT4 was 17.016 +/- 3.847 mol/L. For T3, mean serum concentration was 1.43 +/- 0.825 nmol/L, and mean serum TSH level was 2.412 +/- 2.284 microIU/ml. Variations of serum concentrations of FT4, T3 and TSH with sex, age, or region of origin were not statistically significant. Serum concentration of TSH increased with increased body mass index (BMI). It was 2.073 +/- 1.907 microIU/ml for subjects with BMI of < or = 24.9 Kg/m2, 3.588 +/- 1.495 microIU/ml for subjects with BMI of 25 - 29.9 kg/m2 and 4.450 +/- 0.593 microIU/ml for subjects with BMI > or = 30 kg/m2 (P=0.009). However, BMI had no effect on serum concentrations of FT4 and T3. Serum concentrations of T4, T3 and TSH obtained from this study all differ with the values which are currently used as reference ranges in the country. We recommend a similar study involving a population representative of Ugandans to be conducted so as to establish normal reference values of T4, T3 and TSH for Ugandans. We also recommend BMI of patients to be taken into consideration during interpretation of serum TSH concentrations results.

Effect of clomipramine on the electrocardiogram and serum thyroid concentrations of healthy cats

Clomipramine is a tricyclic antidepressant (TCA) commonly used to treat anxiety related behavioral disorders in companion animals. Tricyclic antidepressants (TCAs) have the potential to cause arrhythmias in humans and companion animals. The effect of the TCAs, clomipramine, and amitriptyline, at therapeutic dosages on cardiac rhythm has been evaluated in dogs. The effect of clomipramine on the cardiac rhythm of cats has not been reported. In Experiment 1, 7 healthy cats were selected to evaluate the effect of clomipramine on their cardiac rhythm using an electrocardiogram. A baseline electrocardiogram was carried out before (Day 0) and repeated (Day 29) after 4 weeks (28 days) of daily clomipramine (10 mg/cat PO) administration. Significant changes in the electrocardiogram were not found after 28 days of daily clomipramine administration. In Experiment 2, 7 healthy cats were enrolled in the study to evaluate the effect of clomipramine administration on the serum thyroid concentrations in cats. Clomipramine (10 mg/cat PO daily) was administered to all cats beginning on Day 1, and continued for 28 days. Serum total thyroxine (T4), triiodothyronine (T3), and free thyroxine (fT4) concentrations were measured before (Day 0) and repeated (Day 29) after 4 weeks (28 days) of daily clomipramine administration. Statistically significant decreases in serum thyroid concentrations (T4, T3, and fT4) were noted between pre and post clomipramine administration. A decrease of 25, 24, and 16% in serum T4, T3, and fT4 concentrations, respectively, may lead to a misdiagnosis of euthyroidism in a subclinical hyperthyroid patient. A longer duration of drug treatment might further suppress thyroid function when used as a single agent, with concomitantly administered drugs, or in conjunction with euthyroid sick syndrome.

Maternal Thyroid Function at 11–13 Weeks of Gestation

Objective: To establish normal ranges of maternal serum thyroid-stimulating hormone (TSH), free thyroxine (FT4) and free triiodothyronine (FT3) at 11–13 weeks of gestation. Methods: Maternal serum concentrations of FT3, FT4, TSH, anti-thyroperoxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies were measured at 11–13 weeks. Normal ranges were constructed from the data of singleton pregnancies with no anti-thyroid antibodies resulting in live births after 34 weeks of phenotypically normal neonates with birth weight above the 5th percentile. Adjustments were made for maternal characteristics found by multiple regression analysis to affect the levels of TSH, FT3 and FT4. Results: 3,592 of the 4,318 pregnancies examined were antibody negative, and in this group serum TSH increased whereas FT3 and FT4 decreased with gestation, and all three were lower in black than in white women. Serum FT3 and FT4 decreased but TSH did not change significantly with maternal age; TSH and FT3 increased whereas FT4 decreased with body mass index; TSH decreased whereas FT3 and FT4 increased with serum free β-hCG. In the antibody-positive group, compared to the negative group, median TSH was higher and median FT3 and FT4 were lower. Conclusion: The study established normal ranges for maternal thyroid function at 11–13 weeks.

Thyroid function in children with growth hormone (GH) deficiency during the initial phase of GH replacement therapy - clinical implications

BackgroundNormal thyroid hormone secretion or appropriate L-thyroxine (L-T4) substitution is necessary for the optimal effect of the growth hormone (GH) administration on growth rate. The decrease of free thyroxine (FT4) levels at recombinant human GH (rhGH) therapy onset has been reported in several studies. The aim of the present study was to evaluate the effect of rhGH administration on thyrotropin (TSH) and FT4 serum concentrations in children with GH deficiency (GHD) during the 1st year of therapy, as well as to assess potential indications to thyroid hormone supplementation in them.Patients and methodsThe analysis involved data of 75 children (59 boys, 16 girls) with disorders of GH secretion (GHD, neurosecretory dysfunction - NSD) and partial GH inactivity (inactGH), who were treated with rhGH for - at least - one year. In all the children, body height and height velocity (HV) were assessed before and after 1 year of therapy, while TSH, FT4, IGF-I and IGFBP-3 before treatment and after 3-6 months and 1 year of treatment. In the patients, who revealed hypothyroidism (HypoT), an appropriate L-T4 substitution was introduced immediately. The incidence of HypoT, occurring during the initial phase of rhGH therapy, was assessed, as well as its influence on the therapy effectiveness.ResultsBefore rhGH substitution, there were no significant differences in either auxological indices or TSH and FT4 secretion, or IGF-I concentration and its bioavailability among the groups of patients. During the initial 3-6 months of rhGH administration, a significant decrease of FT4 serum concentration, together with a significant increase of IGF-I SDS and IGF-I/IGFBP-3 molar ratio was observed in all the studied groups. In 17 children, HypoT was diagnosed and L-T4 substitution was administered. Despite similar IGF-I secretion increase, the improvement of HV presented significantly lower in children with HypoT than in those who remained euthyroid all the time.ConclusionsThe incidence of HypoT during the initial phase of GH treatment in children with GHD and the negative effect of even transient thyroid hormone deficiency on the growth rate should be taken into account.