Effect of pulsatile luteinizing hormone — releasing hormone administration on pituitary — gonadal function in elderly man

Abstract

The effect of short-term pulsatile LHRH administration was studied in 8 healthy subjects ranging from 60 to 81 yr to see if the decrease of pituitary gonadal function could be in part due to changes in the discharge of LHRH from the hypothalamus. Gonadotropin and testosterone (T) secretion was evaluated two weeks before and during LHRH (122-160 ng/kg bw every 120 min sc) infusion. In addition, a bolus dosage of LHRH (50 mu iv) was given both at the beginning and at the end of pulsatile LHRH administration in order to test gonadotrophs sensitivity. A significant increase in gonadotropin levels from day 0 to day 4 was found, and was followed by a subsequent decrease from day 7 to day 14. A slight significant increase in T levels was observed during LHRH administration (p less than 0.01). LH pulses were identified in 5 out of 8 subjects on day 0. On day 14, all the exogenous LHRH pulses were followed by significant LH bursts. There was not a significant decrease in the pituitary LH responsiveness to LHRH test from day 0 to day 14. Our study seems to indicate that pituitary - gonadal unit in normal elderly men can be modulated by pulsatile administration of LHRH. A pulse frequency of LHRH which is probably similar to the physiological one, could induce a slight increase in T levels via qualitative changes in LH activity. We can assume that clinical changes in gonadal activity might also be connected to some disturbances in endogenous LHRH pulsar.

Activation and degeneration during aging: A morphometric study of the human hypothalamus

“…The neurokinin B containing neurons are probably involved in the regulation of the HPG-axis and have been related to menopausal flushes (Rance, 1992). The sensitivity of LH to LHRH did not decrease in elderly males (Giusti et al, 1990;Kaufman et al, 1990Kaufman et al, , 1991. On the other hand, a decreased sensitivity to sex steroid feedback was found in elderly (80 years) postmenopausal women as compared to younger postmenopausal women (55 years) (Rossmanith et al, 1994).…”

Effects of Hypothalamic-Pituitary Aging on Reproduction

“…Postmenopausal women respond to gonadal steroid replacement with youthful gonadotropin dynamics, including positive feedback. 14 The effects of short-term pulsatile GnRH administration on pituitary gonadal function in elderly men was investigated by Giusti et al 49 Healthy subjects ranging from 62 to 81 years of age were studied to determine if decreased pituitary-gonadal function could be due in part to changes in the release of GnRH from the hypothalamus. GnRH was administered exogenously in a pulsatile fashion and significant bursts of LH were elicited in five out of eight subjects, indicating that the anterior pituitary gland of elderly men remains capable of pulsatile administration of GnRH.…”