Effects of thyroid status on pituitary gonadotropin and testicular reserve in men

Arch Androl. Jan-Feb 1997;38(1):85-92. doi: 10.3109/01485019708988535.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 17-alpha-Hydroxyprogesterone / blood
  • Adolescent
  • Adult
  • Estradiol / blood
  • Follicle Stimulating Hormone / blood
  • Gonadotropins, Pituitary / metabolism*
  • Graves Disease / metabolism
  • Humans
  • Hypothyroidism / metabolism
  • Luteinizing Hormone / blood
  • Male
  • Middle Aged
  • Testis / metabolism*
  • Thyroid Gland / physiology*
  • Thyroid Gland / physiopathology
  • Thyrotropin / blood
  • Thyroxine / blood

Substances

  • Gonadotropins, Pituitary
  • Estradiol
  • 17-alpha-Hydroxyprogesterone
  • Luteinizing Hormone
  • Follicle Stimulating Hormone
  • Thyrotropin
  • Thyroxine