Effects of thyroid status on pituitary gonadotropin and testicular reserve in men.
This investigation was conducted to evaluate the effect of thyroid dysfunction on the pituitary-gonadal axis. Ten men with Graves' disease and 5 hypothyroid patients were studied; 10 normal males were studied as a control group. In untreated conditions hyperthyroidism was associated with a normal serum-free testosterone concentration, an increased serum of 17OHP levels, a reduced testosterone response to hCG stimulation, and a hyperresponse of LH to GnRH. These abnormalities reverted after normalization of high FT4 serum levels. Untreated hypothyroid men showed a normal hormone sex response to hCG, but the LH responst to GnRH was reduced, with a tendency to improve after T4 supplementation. There was a strong and significant negative correlation between FT4 and testosterone response, expressed as an area under the curve, and a positive correlation with LH response to GnRH. Despite normal basal free testosterone concentrations, 70% of hyperthyroid and 60% of hypothyroid patients had complaints of decreased libido. The results suggest that thyroid hormones play an important dual pituitary-gonadal effect that is reflected by an impairment of testicular testosterone synthesis associated to hyperresponse to LH in hyperthyroidism and a defective LH response to GnRH in hypothyroidism.
Velázquez
E M
EM
Unidad de Endocrinología, Hospital Universitario de Los Andes, Mérida, Edo. Médira, Venezuela.
Bellabarba Arata
G
G
D019326:17-alpha-Hydroxyprogesterone / Q000097:blood; D000293:Adolescent; D000328:Adult; D004958:Estradiol / Q000097:blood; D005640:Follicle Stimulating Hormone / Q000097:blood; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D006111:Graves Disease / Q000378:metabolism; D006801:Humans; D007037:Hypothyroidism / Q000378:metabolism; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008875:Middle Aged; D013737:Testis / Q000378:metabolism*; D013961:Thyroid Gland / Q000502:physiology* / Q000503:physiopathology; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood
D006065:Gonadotropins, Pituitary; D004958:Estradiol; D019326:17-alpha-Hydroxyprogesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin; D013974:Thyroxine