Lack of effect of moderate hypercalcemia on gonadotropin responsiveness to GnRH

To investigate whether moderate exogenous hypercalcemia influences the release of gonadotropin from human gonadotrophs, 6 normal men were given 50 micrograms GnRH iv on two occasions. On one of these occasions GnRH was administered on an iv background infusion of calcium gluconate, on the other GnRH was injected on a background infusion of saline. The calcium infusion induced moderate hypercalcemia (2.7-2.9 mmol/l) during the GnRH stimulation, whereas normocalcemia prevailed (2.1-2.2 mmol/l) when saline was infused over an identical time period. Similar FSH and LH responses to GnRH were obtained during normo- and hypercalcemia. Moreover, serum testosterone (T) and estradiol (E2) remained unchanged by the hypercalcemia. These results imply that moderate exogenous hypercalcemia does not affect hormone release from pituitary gonadotrophs, and fails to affect peripheral cells involved in the production of T and E2.