TSH, LH and FSH, the three pituitary
glycoprotein hormones, are each composed of a common alpha-subunit and a
hormone specific beta-subunit.
Testosterone is known to regulate all three intact
hormones differently in the rodent. However, there is only one gene encoding the common alpha-subunit. In order to elucidate the effects of
testosterone on TSH subunit synthesis and its regulation of the common alpha-subunit, two in vivo models were studied: castrate rat pituitary was used as a
gonadotropin-enriched tissue; and mouse thyrotropic
tumor was used as a
thyrotropin-enriched tissue. Male castrate rats were treated with
testosterone propionate, 500 micrograms/100 g BW, sc, for 11 days.
Testosterone increased plasma TSH to 131% of control values (P less than 0.02), while plasma LH fell to undetectable levels, and plasma alpha-subunit fell to 14% of control values (P less than 0.001).
Testosterone increased
TSH-beta mRNA to 237% of control values (P less than 0.02), while alpha-subunit
mRNA fell to 20% of control values (P less than 0.001). Hypothyroid mice bearing thyrotropic
tumors were treated with
testosterone propionate, 150 micrograms/100 g BW, sc, for 11 days. In this model plasma
TSH-beta and alpha-subunit concentrations are 1000-fold higher than in non-
tumor bearing animals, and the contribution of pituitary gonadotropes to plasma subunit concentrations is negligible. "Total"
TSH-beta and alpha-subunit concentrations were estimated as one-half of intact TSH plus the respective free subunit concentration.(ABSTRACT TRUNCATED AT 250 WORDS)