Serum insulin-like factor 3 quantification by LC-MS/MS in male patients with hypogonadotropic hypogonadism and Klinefelter syndrome.

The dichotomy between lower INSL3 and higher testosterone concentrations, particularly observed in hCG-treated patients with HH, confirms that INSL3 is a different marker of Leydig cell function than testosterone. However, the clinical application of INSL3 in males with hypogonadism remains unclear.