Reference intervals for serum testosterone, SHBG, LH and FSH in males from the NORIP project

Reference intervals were calculated for male testosterone, SHBG, FSH and LH in serum from 599 individuals in the NORIP study. At 30 years of age, reference limits were calculated to 10.4-32.6 nmol/L testosterone, 13.5-57.4 nmol/L SHBG, 1.93-9.7 IU/L LH and 1.5-10.3 IU/L FSH, at 50 years, 9.3-31.3 nmol/L (testosterone), 18.4-75.6 nmol/L (SHBG), 2.01-10.4 IU/L (LH) and 2.04-12.4 IU/L (FSH), and at 70 years 8.6 to 30.7 nmol/L (testosterone), 27.8-101 nmol/L (SHBG), 2.22-11.2 IU/L (LH) and 2.71-14.2 IU/L (FSH). All age-+related changes were statistically significant. Reference intervals were also calculated for indices derived from testosterone, SHBG and albumin. Free androgen index, simply the ratio between testosterone and SHBG, returned results differing from the other elaborate indices, and the study thus favors use of a more elaborate index such as calculated free testosterone (CFT).