Glucagon-like peptide-1 reduces the pulsatile component of testosterone secretion in healthy males

Authors: Jeibmann, A.; Zahedi, S.; Simoni, M.; Nieschlag, E.; Byrne, M. M.

Source: European Journal of Clinical Investigation, Volume 35, Number 9, September 2005 , pp. 565-572(8)

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Abstract:

Background

Glucagon-like-peptide-1 (7–36) amide (GLP-1), a potent regulator of glucose homeostasis, has been implicated in the control of hypothalamic-pituitary function. In vivo it is a relevant neuroendocrine modulator of gonadotropin-releasing hormone release, suggesting its possible role as a metabolic signal to the reproductive system. The present study was undertaken to establish its effect on luteinizing hormone (LH) and testosterone secretion in nine healthy male volunteers. Materials and methods

Each subject underwent an oral glucose tolerance test to establish LH, testosterone, and GLP-1 responses to glucose. Euglycaemic clamp experiments (6 h) were performed on two occasions with saline or with a constant infusion of GLP-1 (0·4 pmol kg^-1 min ^-1). Blood samples were drawn at 10-min intervals to measure the pulsatile pattern of LH and testosterone secretion. Results

Ingestion of oral glucose resulted in a reduction in plasma testosterone levels at 30 min compared with baseline (P < 0·004) despite unaltered LH levels (P = 0·5). Constant GLP-1 infusion resulted in no change in LH (P = 0·83), testosterone (P = 0·96), follicle stimulating hormone (FSH) (P = 0·86) and leptin levels (P = 0·3). Pulse analysis revealed no significant difference in the number (P = 0·1) or median absolute amplitude (P = 0·3) of the LH pulses. However, there was a significant decrease in the number (3·0 ± 0·6 vs. 1·3 ± 0·4; P < 0·05) and a tendency for increased duration of testosterone pulses (97·4 16·7 vs. 170 27·1 min; P = 0·06). Conclusion

Oral glucose ingestion and intravenous GLP-1 infusion reduce the pulsatile component of testosterone secretion by a mechanism independent of LH release.

Eur J Clin Invest 2005; 35 (9): 565 –572

Keywords: Glucagon-like peptide-1; insulin sensitivity; luteinizing hormone; pulsatile hormone secretion; testosterone

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-2362.2005.01542.x

Affiliations: 1: University of Münster, Institute of Reproductive Medicine, Münster, Germany

Publication date: 2005-09-01