Albrethsen J, Johannsen TH, Jørgensen N, et al. - In the present study, the researchers established a reference range for liquid chromatography–tandem mass spectrometry (LC-MS/MS) of serum insulin-like factor 3 (INSL3) in healthy boys and men and contrasted the correlations of serum INSL3 and testosterone (T) to pubertal stage, lifestyle factors, diurnal variation, body composition, and human chorionic gonadotropin stimulation. According to results, INSL3 rose from levels close to the detection limit (0.03 µg/L) in prepubertal boys to a maximum mean level of 1.3 µg/L (95% CI, 0.9-2.7) in young men (19-40 years of age) and marginally reduced in older men (0.1 µg/L per decade) in a reference range based on LC-MS/MS analysis of serum from 1,073 boys and men. Measurement of serum INSL3 by LC-MS/MS has potential to be a marker for testicular disorders.