Dynamics of prolactin secretion in patients with hypopituitarism and pituitary macroadenomas.

Mild hyperprolactinemia frequently accompanies the hypopituitarism seen in patients with pituitary macroadenomas that do not secrete PRL. We postulated that hypopituitarism in this setting, is primarily caused by compression of the portal vessels and/or pituitary stalk. If this were the case, the dynamics of PRL secretion in this instance would be similar to those in patients with stalk section, dopamine deficiency, or hypothalamic disease. Furthermore, as hypopituitarism in this setting is largely reversible, we postulate that PRL dynamics should also normalize after adenomectomy as a result of the resumption of hypothalamic regulation of pituitary hormone secretion. To test these hypotheses, we examined PRL responsiveness to TRH and the dopamine antagonist, perphenazine (PZ), in patients with pituitary macroadenomas who had hypopituitarism and others with intact pituitary function (controls). Dynamic studies were performed before and 2-3 months after total or subtotal adenomectomy, and the results were correlated with alterations in other pituitary function. In addition, plasma ACTH, cortisol, and PRL levels were measured hours to days after surgery to investigate immediate alterations in pituitary function following surgical decompression. Before surgery, hypopituitary patients had higher serum PRL level than controls (25.5 +/- 12 vs. 11 +/- 3 micrograms/L; P < 0.001). Preoperative dynamic testing of PRL secretion in hypopituitary patients demonstrated an increase in PRL levels after TRH, but not after PZ, administration. In contrast, PRL levels increased appropriately when either stimulus was given to controls. Hours after adenomectomy, PRL levels decreased by 50% in hypopituitary patients (P < 0.0001) and remained so until discharge. In contrast, controls had a transient increase in serum PRL levels after adenomectomy. After surgery, 25 of 43 previously hypopituitary patients recovered part or all pituitary function. Serum PRL levels in the latter subgroup became normal and increased appropriately after stimulation with either TRH or PZ. In contrast, patients who did not recover pituitary function had lower PRL levels that increased minimally after TRH or PZ. The mild increase in serum PRL levels in hypopituitary patients and the discordant responses to stimulation with TRH and PZ suggest dopamine deficiency as a cause of hyperprolactinemia. The drop in serum PRL levels immediately after surgery, at a time when other pituitary hormones (e.g. ACTH), were documented to rise suggests restoration of hypothalamic control over pituitary hormone secretion. The pattern of PRL responses to stimulation in patients recovering function postoperatively was similar to that in controls, although the incremental rise was subnormal.(ABSTRACT TRUNCATED AT 400 WORDS)

Immediate recovery of pituitary function after transsphenoidal resection of pituitary macroadenomas.

Mild hyperprolactinemia frequently accompanies the hypopituitarism associated with pituitary macroadenomas not secreting PRL. Because of this association, hypopituitarism was postulated to be due to compression of portal vessels. We postulate that resumption of hypothalamic control over pituitary function occurs immediately after adenomectomy. To test this hypothesis, we examined pituitary function before and after transsphenoidal adenomectomy in 26 ACTH-deficient patients and 23 subjects with normal adrenal and thyroidal functions (control group). Glucocorticoids, given only to ACTH-deficient subjects, were withdrawn 36 h after surgery. ACTH, cortisol, and PRL levels were measured twice daily in all patients. Both ACTH and PRL levels increased hours after surgery in controls and returned to baseline over 4 days. In all hypopituitary subjects, PRL levels decreased by 50% within hours of adenomectomy and remained so until discharge. ACTH levels, measured simultaneously, increased within hours in 17 of 26 hypopituitary patients, all of whom recovered normal adrenal function before discharge. Nine additional patients had low ACTH levels and required cortisol replacement. The reciprocal changes in PRL and ACTH levels measured simultaneously, hours after surgery, support the hypothesis that hypopituitarism is reversible and largely caused by compression of the protal vessels and the resulting interruption of delivery of hypothalamic hormones. The persistence of hypopituitarism in some patients suggests that ischemic necrosis of the anterior pituitary could limit recovery.