Gender, age, puberty, and BMI related changes of TSH and thyroid hormones in schoolchildren living in a long-standing iodine replete area

The aim of the work was to assess thyroid function in children and adolescents in an iodine replete area and to explore possible effects of age, gender, puberty, and adiposity. Thyrotropin (TSH), total triiodothyronine (T, total thyroxine (T, free thyroxine (FT, and the TTratio were determined for 440 schoolchildren (200 boys and 240 girls), aged 518 years, living in an iodine replete region. Body Mass Index (BMI), BMI standard deviation score (BMI-SDS), and Body Surface Area (BSA) were calculated. In girls there was a negative correlation of TSH, T and FTvalues with age. In boys there was a negative correlation only of Tvalues with age. Girls had lower TSH, T and Tvalues, whereas boys had only lower Tvalues at puberty compared to the prepubertal stage. Girls had lower TSH values than boys (p<0.03) only at puberty. BMI-SDS in boys and girls were 0.21 and 0.03, respectively. BMI-SDS was not related to TSH, T or Tin either gender, whereas it was negatively related to TTratio in boys and to FTin girls. We conclude that estrogens may exert a suppressive effect on the pituitary-thyroid axis after puberty. TSH values are not correlated with BMI-SDS, whereas TTratio in boys and FTin girls are negatively correlated with BMI-SDS. © Georg Thieme Verlag KG Stuttgart New York

Obesity and attenuated adiposity rebound in children with congenital hypothyroidism. Normalization of BMI values in adolescents

An earlier adiposity rebound, suggestive of adult obesity, has been reported in children with congenital hypothyroidism. We undertook this study to evaluate the effect of congenital hypothyroidism on: 1) the timing of adiposity rebound, 2) the long-term prognosis of BMI status, and 3) the factors potentially affecting adiposity in subjects with congenital hypothyroidism. We found that in children with congenital hypothyroidism the BMI values were higher during the first years of life compared to normal population, but subsequently normalized. After the initial rise of BMI, the decline (nadir) and subsequent rise (adiposity rebound), usually occurring in normal children at an age greater than 30 months, was less evident in our group of children with congenital hypothyroidism. The severity of hypothyroidism affected BMI values at 6 and 12, but not at 36 months of age. In conclusion, in children with congenital hypothyroidism, 1) the high BMI values in early childhood normalize in adolescence, and 2) the normally expected BMI fluctuations during the first years of life are attenuated. These findings constitute indirect evidence that thyroid function during fetal and neonatal life affects BMI status during the first years of life

Adrenal Steroids in Female Hypothyroid Neonates: Unraveling an Association between Thyroid Hormones and Adrenal Remodeling

Context: The adrenal gland undergoes substantial remodeling during the neonatal period, an essential developmental process that remains incompletely understood. With respect to control over the remodeling process and, specifically, the role of thyroid hormones (THs), no human studies have been published. The effects of both hypo-and hyperthyroidism have only been evaluated in adults, focusing on the mature adrenal. Recent studies have identified expression of the TH receptor β1 in the mouse adrenal X-zone and have demonstrated that TH administration could alter the postnatal adrenal remodeling process. Objective: To address whether THs influence adrenal steroid profiles and adrenal remodeling during the neonatal period. Methods: We compared the adrenal steroid profile of a naturally occurring prototype, female neonates with severe congenital hypothyroidism (CH) (n = 22, upon diagnosis of CH), with that of euthyroid neonates (n = 20). Results: Significantly higher levels of adrenal steroids (17-OH-progesterone, dehydroepiandrosterone sulfate, Δ4-androstenedione, and testosterone) were measured in neonates with severe CH compared with euthyroid neonates and returned to within normal range after euthyroid state had been established on l-thyroxine replacement therapy, whereas cortisol levels did not differ. TSH values in the CH group were positively correlated with circulating adrenal steroids, whereas free T4 levels were negatively correlated with circulating adrenal steroids. Conclusions: The hormonal profile of female neonates with severe CH suggests a more active adrenal fetal zone compared with control subjects. These data indirectly associate THs with the adrenal remodeling and maturation process in humans. Based on our results, we suggest that severe hypothyroidism decelerates the involution of the adrenal fetal zone that normally occurs postnatally. © 2019 Endocrine Society