Thyrotropin secretion profiles are not different in men and women

Context: The hypothalamo-pituitary-thyroid axis in women may differ from that in men. Previous reports have shown an almost 2-fold increased response to TRH in females compared with males. Objective: We analyzed TSH profiles in healthy men and women to delineate differences in the hypothalamo-pituitary- thyroid system. Subjects and Intervention: The subjects, 24 men (mean age 44 ± 3 yr) and 22 women (mean age 42±3 yr) underwent a 24-h study with blood sampling intervals of 10 min. Premenopausal women were investigated in the early follicular phase of the cycle. Methods: Serum TSH concentration profiles were analyzed with a newly developed automated deconvolution program, approximate entropy, and cosinor regression. Results: Basal and pulsatile TSH secretion, and also pulse frequency, hormone half-lives, and secretory mode were indistinguishable in the two genders. There were no differences in diurnal variation, and the times of maximal secretion coincided. Approximate entropy, reflecting secretory regularity, was not different between men and women. In women but not men, TSH secretion was dependent linearly on age. Conclusions: TSH secretion is gender invariant and depends on age in women only.