Effects of galanin on growth hormone and prolactin secretion in anorexia nervosa.

Galanin (GAL) elicits growth hormone (GH) release in normal subjects through interaction with hypothalamic somatostatin. GAL also stimulates GH-releasing hormone (GHRH) secretion in vitro. In rats, GAL is able to stimulate prolactin (PRL) release, but this effect is not clear in humans. We have thus investigated GAL effects on GH and PRL release in patients with anorexia nervosa (AN), known to have altered regulation of the GH-insulin-like growth factor axis and PRL dynamics, and compared the effects of GHRH and GAL on GH and PRL secretion in AN and normal healthy subjects. Eight women with AN (15 to 27 years; body mass index [BMI], 17 to 19.5 kg/m2) were treated with (1) GHRH 50 microg intravenous (IV) injection, (2) porcine GAL 500 microg infusion from -10 to +30 minutes, and (3) 135-minutes saline infusion as a control, respectively. Both peptides induced a significant increase in plasma GH in AN patients (peak level, 27.41 +/- 5.50 microg/L after GAL and 18.97 +/- 2.67 microg/L after GHRH). When data for AN patients and the control group were compared, GH peak levels after GAL were significantly higher in AN patients (27.41 +/- 5.50 v 13.64 +/- 2.32 microg/L), while GH peak levels after GHRH were not different between the 2 groups (18.97 +/- 2.67 v 15.98 +/- 3.88 microg/L). PRL levels significantly increased after both GHRH (peak, 11.70 +/- 2.80 microg/L) and GAL (peak, 18.02 +/- 5.10 microg/L) treatment in AN patients, but not in normal subjects. We conclude that GAL stimulates exaggerated GH release in AN patients as compared with normal controls, suggesting a dual hypothalamic interaction via both an increase in endogenous GHRH and a decrease in somatostatin secretion. Finally, GAL may act as a PRL secretagogue in AN patients.

Baseline and stimulated catecholamine secretion in normotensive patients with active acromegaly: acute effects of continuous octreotide infusion.

OBJECTIVE: Alterations in catecholamine plasma levels may contribute to the cardiovascular complications of acromegaly. Since few data are available on the catecholamine secretory dynamics in active acromegaly and no evidence exists on catecholamine variations during GH decrease, we studied acromegalic patients before and during octreotide administration. METHODS: We evaluated the catecholamine responses to upright posture and a cold pressure test (CPT) in 11 acromegalic (A) patients before and during continuous administration of octreotide (500 microgram/24h by s.c. pump) compared with 11 normal (N) subjects. RESULTS: All the acromegalic patients showed left ventricular cardiac hypertrophy. The cardiovascular responses to upright posture were similar between normal subjects and acromegalics both before and during octreotide treatment. The basal levels of norepinephrine (NE) were significantly higher in A patients compared with N subjects (423+/-45 vs 264+/-32pg/ml, P<0. 05) and decreased during therapy (291+/-32pg/ml; P<0.01). The increase in plasma NE during upright posture was significantly lower in A than in N subjects (P<0.01), but was restored to normal during octreotide treatment. CPT increased systolic and diastolic blood pressure, pulse rate and NE plasma levels in N (P<0.05) but not in A subjects both before and during octreotide treatment. CONCLUSIONS: Our data demonstrate the presence of increased basal NE levels in acromegalic patients with a defective sympathetic response to stimuli. Short-term octreotide infusion is able to induce a reduction in the basal levels of NE and a normalization of the catecholamine response to posture.

Modulation by galanin of growth hormone and gonadotropin secretion from perifused pituitary and median eminence of prepubertal male calves.

Galanin is widely distributed in the peripheral and central nervous system and has been indicated as a putative hypothalamic-hypophysiotropic hormone. This study was performed to investigate the effects of galanin on both growth (GH) and luteinizing hormones (LH) from pituitaries of young male calves. Pituitary slices (P, 500 microm in thickness) were perfused alone or coincubated with median eminence terminals (ME) in DMEM-F12 plus BSA 0.1% and antibiotics. The perifusion chambers were kept in equilibrium for 150 min, and medium samples were collected every 10 min for 240 min and stored at -20 degrees C until the measurement of LH and GH levels. Basal GH release increased up to 60% after galanin infusion (p < 0.01 vs. baseline levels) for 60 min in P alone; in P + ME coincubation, galanin-stimulated GH secretion was further increased by up to 200%. Basal LH release in chambers with P was significantly increased (up to 25%; p < 0.05) for 70 min after galanin infusion; P + ME coincubation showed a galanin-mediated increase in LH release of up to 50%. GH and LH responsiveness to exogenous GH-releasing hormone and gonadotropin-releasing hormone was not significantly modulated by galanin in our experimental model. In conclusion, galanin is demonstrated to have a significant stimulatory role in the secretion of GH and LH, with a combined action at both the hypothalamic and pituitary levels. ......................