Osteocalcin increase after bariatric surgery predicts androgen recovery in hypogonadal obese males

Bone modulates testis function through osteocalcin (OCN) production. This paper assesses the association between serum OCN and androgen production recovery in morbidly obese males at 9 months after bariatric surgery.

A cohort of n=103 obese males with mean±s.d. body mass index (BMI) 47.7±8.2 kg m(-2), age 42±11 years, consisting of n=76 patients undergoing gastric bypass and n=27 in the waiting list for surgery.

At 9 months from surgery, a significant increase was observed in mean±s.d. total OCN (tOCN=10.4±10.3 ng ml(-1), P<0.001) and undercarboxylated OCN (ucOCN=5.4±3.7 ng ml(-1), P<0.001), total testosterone (TT, 5.6±6.5 nM, P<0.001) and calculated free testosterone (cFT, 0.035±0.133 nM, P<0.006), sex hormone binding globulin (SHBG, 21.2±16.7 nM, P<0.001) and decrease in estradiol (E2, -30.1±51.9 pM, P<0.001) levels only in operated patients, with a significant reduction in BMI (24%) and waist (20%). A positive correlation existed between tOCN and ucOCN (age-adjustment (age-adj.): β=0.692, P<0.001) and their variations (age-adj.: β=0.629, P<0.001) after surgery. Multivariate analysis in operated patients showed a significant positive association between variations in tOCN and TT (age-adj.: β=0.289, P=0.012), SHBG (age-adj.: β=0.326, P=0.005) but not with cFT variation. tOCN, but not luteinizing hormone (LH) variation was the only significant predictive factor of cFT recovery in the hypogonadal (TT<12 nM) operated subjects even after age- and BMI-adjustment (adj.: β=0.582, P<0.05). cFT improvement was significantly higher when considering operated patients with tOCN increase (0.045±0.123 vs -0.02±0.118 nM, P=0.015), hypogonadism (0.059±0.111 vs -0.059±0.138 nM, P=0.002) and younger than 35 years (0.102±0.108 vs -0.019±0.123 nM, P=0.009).

OCN recovery observed after bariatric surgery is significantly associated with cFT improvement independently of BMI variation and age in hypogonadal morbidly obese males.