Long-term basal and dynamic evaluation of hypothalamic-pituitary-adrenal (HPA) axis in acromegalic patients

Objective: Long-term effects of trans-naso-sphenoidal surgery (TNS) or long-acting somatostatin analogs (SSA) on the function of hypothalamic- pituitary-adrenal (HPA) axis have been poorly investigated. Aim of this study was to evaluate HPA axis integrity during the follow-up in patients with GH-secreting pituitary adenomas and preserved HPA function post-TNS or prior SSA. Design and patients: This retrospective study investigated 36 acromegalic patients (16M and 20F, age: 47 ± 13 years), 20 of whom cured by TNS and 16 controlled by SSA therapy (12 previously operated and 4 in primary medical therapy), before and after long-term follow-up (median: 72 months, range: 12-240). No patient previously underwent radiotherapy. Measurements: HPA function was studied by morning circulating cortisol and ACTH levels, 24-h urinary free cortisol (UFC) and cortisol response to low-dose short Synacthen test (LDSST, 1 μg) with a peak > 500 nmol/l as cut-off for normal function. Results: Serum basal cortisol, ACTH and UFC levels were in the normal range and did not significantly change over time. As far as the cortisol peak after LDSST is concerned, 12 patients (32%, 8 TNS and 4 SSA) developed biochemical hypoadrenalism. None of the patients in primary medical therapy showed cortisol peak < 500 nmol/l. No significant correlations between HPA axis deterioration and follow-up duration, serum GH/IGF-I levels, occurrence of other pituitary deficiencies, presence of secondary empty sella, changes in tumour or residual volume were observed. Conclusions: The HPA axis function must be carefully monitored over the time by dynamic testing in all acromegalic patients, independently from the type of treatment.