Effect of pyridostigmine on the hydrocortisone-mediated decrease of circulating growth hormone levels in acromegaly

The aims of our study were to investigate the effect of the acetylcholinesterase inhibitor pyridostigmine (PD) administration on growth hormone (GH) secretion in acromegaly and to investigate the effects of PD on GH levels following an i.v. infusion of hydrocortisone in acromegaly. We studied five adult patients with active acromegaly, three men and two women with a mean age of 60 +/- 5 years (range 47-71 years) and a mean BMI of 27 +/- 0.7 kg/m2 (range 24-28 kg/m2). All the patients underwent: 1) placebo, 2 tablets po or 2) PD, 120 mg po, at time -60 plus a bolus i.v. injection of 100 mg hydrocortisone succinate in 2 ml saline at time 0 followed by an i.v. infusion of 250 mg hydrocortisone succinate in 250 ml saline from 0 to 120 min, or 3) PD, po or 4) placebo, po at time -60 plus a bolus i.v. injection of 2 ml saline followed by an i.v. infusion of 250 ml saline from 0 to 120 min. Serum GH values did not significantly change after PD administration compared to those during placebo treatment and with respect to baseline levels. In all of the acromegalic patients during hydrocortisone succinate infusion, GH values clearly decreased with respect to basal levels in varying degrees, with a nadir between 90 and 180 minutes after the beginning of hydrocortisone infusion.(ABSTRACT TRUNCATED AT 250 WORDS)