Effect of a new LH-RH analogue (D-Ser(TBU)6-EA10-LH-RH) on gonadotrophin and gonadal steroid secretion in men.

The effect of a new analogue of the gonadotrophin-releasing hormone LH-RH, D-Ser(TBU)6-EA10-LH-RH, on the secretion of LH, FSH, as well as testosterone, oestradiol, HGH, prolactin, TSH, and cortisol was studied in normal men. The same subjects were injected intravenously in 4-day intervals with 1.0, 2.5, 5.0, and 10.0 mug of this substance. A significant LH but no FSH release was seen after doses of 1.0 and 2.5 mug LH-RH analogue, while after 5.0 and 10.0 mug dose-dependent increases of LH and imposed elevations of FSH were observed. Peak levels of LH were reached after 30 min, those of FSH after intravenous injection after 120 min. LH and FSH remained elevated for 8-10 h. LH peak levels after 5 mug of LH-RH analogue were comparable to those seen after injection of 100 mug of the decapeptide LH-RH. Following the release of LH and FSH after doses of 5.0 and 10.0 mug LH-RH analogue, there was a late stimulating effect in testosterone and oestradiol secretion. HGH, TSH, prolactin, and cortisol were not influenced by the LH-RH analogue.