Effect of galanin on the growth hormone response to growth hormone-releasing hormone in acromegaly

Giustina, Andrea; Schettino, Maurizio; Bodini, Corrado; Doga, Mauro; Licini, Massimo; Giustina, G

doi:10.1016/0026-0495(92)90098-u

Cited by 11 publications

(8 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Dynamic pituitary tests are not helpful in distinguishing acromegalic patients with pituitary tumors from those harboring extrapituitary tumors [59]. GH responses to TRH do not distinguish the various forms of acromegaly, as GH levels are usually stimulated in most patients and its diagnostic use is not cost-effective.…”

Section: Diagnosismentioning

confidence: 98%

Neuroendocrine tumors secreting growth hormone-releasing hormone: Pathophysiological and clinical aspects

et al. 2006

Self Cite

View full text Add to dashboard Cite

Hypothalamic GHRH is secreted into the portal system, binds to specific surface receptors of the somatotroph cell and elicits intracellular signals that modulate pituitary GH synthesis and/or secretion. Moreover, GHRH is synthesized and expressed in multiple extrapituitary tissues. Excessive peripheral production of GHRH by a tumor source would therefore be expected to cause somatotroph cell hyperstimulation, increased GH secretion and eventually pituitary acromegaly. Immunoreactive GHRH is present in several tumors, including carcinoid tumors, pancreatic cell tumors, small cell lung cancers, endometrial tumors, adrenal adenomas, and pheochromocytomas which have been reported to secrete GHRH. Acromegaly in these patients, however, is uncommon. The distinction of pituitary vs. extrapituitary acromegaly is extremely important in planning effective management. Regardless of the cause, GH and IGF-1 are invariably elevated and GH levels fail to suppress (<1 microg/l) after an oral glucose load in all forms of acromegaly. Dynamic pituitary tests are not helpful in distinguishing acromegalic patients with pituitary tumors from those harbouring extrapituitary tumors. Plasma GHRH levels are usually elevated in patients with peripheral GHRH-secreting tumors, and are normal or low in patients with pituitary acromegaly. Unique and unexpected clinical features in an acromegalic patient, including respiratory wheezing or dyspnea, facial flushing, peptic ulcers, or renal stones sometimes are helpful in alerting the physician to diagnosing non pituitary endocrine tumors. If no facility to measure plasma GHRH is available, and in the absence of MRI evidence of pituitary adenoma, a CT scan of the thorax and abdominal ultrasound could be performed to exclude with good approximation the possibility of an ectopic GHRH syndrome. Surgical resection of the tumor secreting ectopic GHRH should be the logical approach to a patient with ectopic GHRH syndrome. Standard chemotherapy directed at GHRH-producing carcinoid tumors is generally unsuccessful in controlling the activated GH axis. Somatostatin analogs provide an effective option for medical management of carcinoid patients, especially those with recurrent disease. In fact, long-acting somatostatin analogs may be able to control not only the ectopic hormonal secretion syndrome, but also, in some instances, tumor growth. Therefore, although cytotoxic chemotherapy, pituitary surgery, or irradiation still remain available therapeutic options, long-acting somatostatin analogs are now preferred as a second-line therapy in patients with carcinoid tumors and ectopic GHRH-syndrome.

show abstract

Section: Diagnosismentioning

confidence: 98%

Neuroendocrine tumors secreting growth hormone-releasing hormone: Pathophysiological and clinical aspects

et al. 2006

Self Cite

View full text Add to dashboard Cite

show abstract

“…There is evi dence suggesting that the effect of galanin is mediated at the hypothalamic level since intracerebroventricular ad ministration of p-galanin in ovariectomized rats induces a clear-cut dose-dependent increase in GH secretion [34], Since experimental observations indicate an innervation of somatostatin neurons by galanin cells in the hypothala mus [41 ], it has been suggested that galanin is able to stim ulate GH secretion via a decrease in hypothalamic soma tostatin tone [42], On the other hand, galanin infusion not only causes an increase in baseline GH levels in both male and female humans [35,43]. but it is also a potent enhanc er of the GH response to GHRH in males [44] and in young women [22], Finally, some authors have suggested that galanin may be a direct, if rather weak, stimulus of GH secretion directly at the pituitary level, at least in the rat [18], Our study leads us to hypothesize that, in our model, galanin-mediated GH release occurs independent ly of hypothalamic somatostatin. Interestingly, we have observed a direct effect of galanin on pituitary GH release from tissue slices which mimic the in vivo physiology bet ter than cell cultures, but other factors may be involved such as paracrine ones inside the pituitary, as has been reported for other peptides [45], Our findings show for the first time that, in a 'physiological' in vitro model, the GHstimulating action of galanin is enhanced by an interac tion between median eminence terminals and pituitary.…”

Section: Discussionmentioning

confidence: 99%

Modulation by Galanin of Growth Hormone and Gonadotropin Secretion from Perifused Pituitary and Median Eminence of Prepubertal Male Calves

Baratta

Saleri²,

Mascadri³

et al. 1997

Neuroendocrinology

Self Cite

View full text Add to dashboard Cite

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 µm 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 °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.

show abstract

“…6 No dynamic tests are helpful in differentiating the causes. 7 Among all, plasma GHRH is the most precise and costeffective test for the diagnosis of ectopic GHRH causing acromegaly. Plasma GHRH levels are usually elevated in patients with peripheral GHRHsecreting tumours, and are normal or low in patients with pituitary acromegaly.…”

Section: Discussionmentioning

confidence: 99%

An unusual cause of acromegaly

et al. 2014

View full text Add to dashboard Cite

Effect of galanin on the growth hormone response to growth hormone-releasing hormone in acromegaly

Cited by 11 publications

References 30 publications

Neuroendocrine tumors secreting growth hormone-releasing hormone: Pathophysiological and clinical aspects

Neuroendocrine tumors secreting growth hormone-releasing hormone: Pathophysiological and clinical aspects

Modulation by Galanin of Growth Hormone and Gonadotropin Secretion from Perifused Pituitary and Median Eminence of Prepubertal Male Calves

An unusual cause of acromegaly

Contact Info

Product

Resources

About