SHBG and obesity due to melanocortin 4 receptor deficiency: While TT may reflect adaptation to obesity-associated lowering of SHBG, it is important to emphasize that 97 % of our study population had a baseline free testosterone (calculated from LCMS/MS total testosterone) of less than 243 pmol/L, the lower limit reported for healthy young men [4], and 89 % a level of less than 220 pmol/L, the cut-off for late onset hypogonadism [35].