Longitudinal Increases in Serum Insulin-like Factor 3 and Testosterone Determined by LC-MS/MS in Pubertal Danish Boys

Serum concentrations of the peptide hormone insulin-like factor 3 (INSL3) is a candidate marker for improved distinction between constitutional delay of growth and puberty (CDGP) and permanent hypogonadotropic hypogonadism (HH) in boys.

To assess the possible diagnostic role of LC-MS/MS-based INSL3 measurements as a marker of imminent puberty by comparison with testosterone (T) and luteinizing hormone (LH) levels in serum longitudinally collected from 18 healthy boys throughout puberty.

The first increase in serum LH was detected on average 4 months earlier, as compared with the first observed increases in INSL3 and T. When comparing the 2 testicular hormones only, we found that in 22% (4 of 18) of the boys the first increase in serum INSL3 was observed prior to the first observed increase in T, whereas in 44% (8 of 18) the first increase in T was observed before the first observed increase in INSL3. In the remaining 6 boys, the 2 testicular hormones showed the first increase at the same examination.

In some boys with delayed puberty, the first indication of testicular maturation may be detectable by observing serum INSL3. Further studies of LC-MS/MS determination of serum INSL3 in patients with CDGP and HH are warranted.