The effect of synthetic luteinizing hormone-releasing factor on plasma lh levels in pituitary disease

Synthetic luteinizing hormonereleasing factor was administered intravenously in a dose of 150 M-g to 15 normal subjects, 24 subjects with pituitary tumors, 5 subjects with Sheehan's syndrome and 4 subjects with idiopathic hypogonadotropic hypogonadism to evaluate pituitary secretory reserve for LH. In normals plasma LH rose in all individuals from a mean level of 6.4 mlU/ml (range 3.7-10) to a mean level of 55 mlU/ml (range 16-230). In 5 subjects with pituitary tumors who maintained normal gonadotropin secretion, plasma LH levels following LRF rose normally in 4 indicating normal secretory reserve in most subjects. In all subjects with Sheehan's syndrome and idiopathic hypogonadotropic hypogonadism and in 17 of 19 subjects with a pituitary tumor who had reduced gonadotropin secretion plasma LH levels following LRF did not rise or rose subnormally. These data suggest that decreased responsiveness to LRF was the cause of hypogonadotropism in these subjects. In 2 subjects with hypogonadotropism secondary to a pituitary tumor, plasma LH rose normally following LRF. The explanation of decreased gonadotropin secretion in these subjects is not clear but could be the result of defective endogenous LRF production.