To test whether concentrations of estradiol and testosterone predict GH responses to mechanistically distinct secretagogues in healthy older adults, we studied 16 volunteers (n = 10 men, n = 6 women, age 49-72 yr) in each of six randomly ordered sessions as follows: 1) saline; 2) L-arginine; 3) aerobic exercise; 4) GHRH; 5) GH-releasing peptide (GHRP)-2; and 6) somatostatin-induced rebound. Statistical comparisons disclosed that stimulus type (P < 0.001) and the interaction between gender and stimulus type (P = 0.023) determine GH secretion. In women, each secretagogue, except exercise and somatostatin-induced rebound, stimulated GH secretion by 2.6- to 6.4-fold over saline/rest (P < 0.023). In men, somatostatin-induced rebound drove GH secretion by 4.6-fold (P = 0.004), exercise by 16-fold (P < 0.001), and other secretagogues by 18- to 109-fold over saline/rest (each P < 0.001). Gender comparisons disclosed greater GH secretion in men than women after somatostatin-induced rebound (P = 0.008) and GHRP-2 injection (P < 0.001) and conversely greater GH secretion in women than men after saline (P = 0.013). Regression analysis showed that individual concentrations of estradiol (r = 0.80, P = 0.002) and testosterone (r = 0.63, P = 0.008) and their combination (r = 0.86, P < 0.001) strongly predict responses to GHRP-2 only. We conclude that among healthy middle-aged and older adults, the action of GHRP is uniquely determined by gender and physiological concentrations of testosterone and estradiol.
Contributions of gender and systemic estradiol and testosterone concentrations to maximal secretagogue drive of burst-like growth hormone secretion in healthy middle-aged and older adults / J.D. Veldhuis, J.T. Patrie, K.T. Brill, J.Y. Weltman, E.E. Müller, C.Y. Bowers, A. Weltman. - In: THE JOURNAL OF CLINICAL ENDOCRINOLOGY AND METABOLISM. - ISSN 0021-972X. - 89:12(2004), pp. 6291-6296.
|Titolo:||Contributions of gender and systemic estradiol and testosterone concentrations to maximal secretagogue drive of burst-like growth hormone secretion in healthy middle-aged and older adults|
|Settore Scientifico Disciplinare:||Settore BIO/14 - Farmacologia|
|Data di pubblicazione:||2004|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1210/jc.2004-0644|
|Appare nelle tipologie:||01 - Articolo su periodico|