Inhibitory effects on gonadotrophin secretion and gonadal function in men during chronic treatment with a potent stimulatory luteinizing hormone-releasing hormone analogue.

Long-term treatment with the potent and long-acting stimulatory luteinizing hormone-releasing hormone (LRH) analogue D-Ser(TBU)6-EA10-LRH was given to 4 healthy men to study its effects on pituitary gonadotropin secretion and gonadal function. Five micrograms of the LRH agonist was self-administered sc once daily over 17 weeks. Weekly basal blood samples were obtained for determination of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolacting (PRL) and testosterone. The gonadotrophin responses to the LRH analogue were also determined during the treatment period. LRH tests were performed after treatment. Seminal fluid specimens were collected during and after treatment. A reduction of the basal serum gonadotrophin and testosterone levels were observed during the treatment period. The FSH and LH responses to the analogue were also diminished. After discontinuation of treatment the gonadotrophin and testosterone concentrations returned to pre-treatment levels within a week. The PRL levels and the seminal fluid specimens did not show any significant changes during the study period. The results suggest that chronic treatment with D-Ser(TBU)6-EA10-LRH has an inhibitory effect on the pituitary gonadotrophin secretion in healthy men. It seems likely that the reduced testosterone level is secondary to the diminished gonadotrophin secretion.