NEW YORK (Reuters Health) - Insulin-like factor 3 (INSL3) is a circulating hormone, secreted by Leydig cells of the testis, that may have a systemic function, Italian investigators report.
Dr. Carlo Foresta, at the University of Padova investigated the role of the hormone and its receptor in adults. In normal men, the serum concentration of INSL3 averages 562.3pg/mL, the authors report in the December issue of the Journal of Clinical Endocrinology and Metabolism. Levels are significantly lower in normal women (99.5 pg/mL).
In untreated orchidectomized men, men with Klinefelter’s syndrome, and infertile men with severe hypospermatogenesis, levels average 69.5, 157.5 and 289 pg/mL, respectively.
These findings suggest that INSL3 is almost exclusively of testicular origin, and its concentration seems to reflect the functional status of Leydig cells, the authors note. The intermediate concentrations in patients with severe hypospermatogenesis suggest the presence of mild Leydig cell dysfunction.
The authors also found significant positive correlations between serum INSL3 and luteinizing hormone (LH) concentrations and testosterone concentrations, suggesting that “the production of INSL3 by the Leydig cells is related to LH, the main regulator of Leydig cell function.”
Polymerase chain reaction testing showed that the INSL3 receptor is present in the hypophysis, as well as the testis and kidney, but is absent in the liver and prostate.
“Taken together, these data suggested that a pituitary-testicular axis involving LH and INSL3 may exist,” the authors write.
“Additional roles of this hormonal system in adult men are plausible, with it acting both as a paracrine mediator on germ cells and as an endocrine factor elsewhere.”
In fact, they suggest that “INSL3 concentrations may reflect the functional status of Leydig cells possibly better than testosterone concentrations.”
Source: J Clin Endocrinol Metab 2004;89:5952-5958. [ Google search on this article ]
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