SPONTANEOUS THYROTROPIN AND CORTISOL SECRETION INTERACTIONS IN PATIENTS WITH NONCLASSICAL 21-HYDROXYLASE DEFICIENCY AND CONTROL CHILDREN

Both exogenous and endogenous hypercortisolism result in reduced TSH s ecretion and mild hypothyroidism. However, little is known about the r elation between endogenous TSH and cortisol secretion under physiologi cal or slightly disturbed conditions. To examine this, we evaluated th e pulsatility and circadian rhythmicity and time-cross-correlated the 24-h secretory patterns of cortisol and TSH in eight prepubertal child ren with nonclassical congenital adrenal hyperplasia (NCCAH) and eight age-matched short normal children. In both groups, TSH and cortisol w ere secreted in a pulsatile and circadian fashion, with a clear noctur nal TSH surge. Although no difference in mean 24-h TSH levels was obse rved between the two groups, daytime TSH levels were lower in the NCCA H group than in control children (P < 0.05). The cross-correlation ana lysis of the 24-h raw data showed that TSH and cortisol were negativel y correlated, with a 2.5-h lag time for both groups, with cortisol lea ding TSH. This correlation might reflect a negative glucocorticoid eff ect exerted on the hypothalamic-pituitary-thyroid axis under physiolog ical conditions. A significant positive correlation with TSH leading c ortisol was observed at 8.5 and 5.5 h lag times for the control and NC CAH groups, respectively. The substantially shorter lag time of this p ositive correlation in NCCAH children than in controls suggests that i n the latter, the nocturnal TSH peak occurs temporally closer to their compromised morning cortisol peak. These data indicate that the hypot halamic-pituitary-adrenal axis has a primarily negative influence on e ndogenous TSH secretion and that even mild disturbances in cortisol bi osynthesis are associated with slight alterations in TSH secretion.