The effect of short-term treatment with recombinant human thyroid-stimulating hormones on leydig cell function in men

High levels of thyroid-stimulating hormone (TSH) have been implicated as a cause for precocious puberty associated with severe long-standing juvenile hypothyroidism. Recombinant human thyroid-stimulating hormone (rhTSH) is available for the management of patients with thyroid carcinoma, and after its administration the serum TSH levels are similar to those observed in hypothyroid infants with precocious puberty. Our objective was to investigate whether rhTSH increased testosterone secretion in adult males with differentiated thyroid carcinoma. Thirty-one adult Caucasian men, ages 18-59 years, with differentiated thyroid carcinoma were studied. While continuing on thyroid hormone therapy, patients received 0.9 mg of rhTSH 24 hours apart. Blood samples were obtained before the first rhTSH dose (day 1) and at 24 hours (day 3) and 72 hours (day 5) after the second rhTSH dose. TSH, total testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were determined. Serum TSH levels were increased at day 3 (129.2 +/- 5.7 micro U/mL) versus day 1 (0.6 +/- 0.2 micro U/mL) but observed differences in total testosterone, LH and FSH throughout the study were not statistically significant. In conclusion, short-term elevations in serum TSH levels in the range reported in hypothyroid boys with precocious puberty did not increase serum testosterone levels in adult men.