Kinetics of steroid responsiveness to hCG during chronic inhibition of testicular function by GnRH analogue.

The effect of daily injections of D-Ser-(TBU)6-LRH-EA10 (GnRH analogue (GnRH-A) 100 micrograms sc) on serum testosterone (T), 17 alpha-hydroxyprogesterone (17OHP) and oestradiol-17 beta (E2) was studied in 4 men. During GnRH-A therapy T, 17OHP and E2 were markedly decreased by the end of the second month. Continuous long-term administration of GnRh-A inhibited testicular function. To test whether the biosynthetic pathway was affected by the regimen, a bolus of 2000 U hCG was given to each subject after 10 months of therapy. Evaluation of the kinetics of steroid responsiveness showed a significant release of T in response to the trophic stimulus, with little or no elevation of serum 17OHP and E2. The response seen in these treated men appeared similar to that found in hypogonadotrophic men and prepubertal boys.