Plasma ACTH levels and beta-endorphin-like immunoreactivity following administration of luteinizing hormone-releasing hormone in Nelson's syndrome.

The effect of LH-RH (25 micrograms as a single i.v. bolus) on plasma corticotropin (ACTH) levels and beta-endorphin-like immunoreactivity was studied at 30 and 60 min in eight women with Nelson's syndrome. Plasma ACTH concentrations increased in three of them, while beta-endorphin-like immunoreactivity, measured in six cases, rose significantly at 30 min in all the patients under investigation. In the control group containing seven women with Nelson's syndrome, placebo (0.9% sodium chloride) administration did not induce any significant changes in ACTH concentrations or in beta-endorphin-like immunoreactivity. Our results suggest that a paradoxical stimulatory influence of LH-RH on pituitary Nelson's adenomas may play an important role in the adenoma hormonal activity and, perhaps, growth. Such an effect could be responsible for a rapid development of some pituitary neoplasms during pregnancy.