SHBG as a men's osteoporosis marker and obesity surgery
Sex hormone-binding globulin (SHBG), estradiol, and bone turnover markers in male osteoporosis. This is an interesting study comparing men with osteoporosis to age-matched controls in France. See: Bone. 2004 Jun;34(6):933-9, Lormeau C and others, PMID: 15193539. Using 65 men with osteoporosis (T score <-2.5 in the lumbar spine or at the femoral neck), the authors found 33 subjects to have idiopathic osteoporosis (no known cause) and 32 with a detectable cause for the problem. Measurements were made of total estradiol, total testosterone, and their carrier protein: SHBG. Additionally various markers of bone remodeling were also measured. The two for bone formation were osteocalcin (OC) and bone alkaline phosphatase (BAP), and the two for bone resorption were type I C-terminal telopeptide (ICTP) and serum C-telopeptide of type I collagen (sCTX). Although the estradiol level was not different between men with osteoporosis and controls, SHBG levels were significantly higher in individuals with osteoporosis (P <0.01), and this difference persisted after adjustment for body mass index. Additionally SHBG concentration correlated strongly with sCTX (P < 0.01) and logistic regression analysis showed SHBG to be significantly associated with the presence of fractures. The authors comment, "This study therefore suggests that SHBG may play a key role in male patients with idiopathic or secondary osteoporosis. It shows that SHBG concentration is increased with middle-aged men with osteoporosis and is correlated with hip, spine BMD, and sCTX levels. Finally, our findings are in agreement with previous studies which suggest that serum SHBG is a new biological marker of fracture risk in men." Thus, SHBG should be added to the diagnostic testing battery when checking men for osteoporosis, especially for its fracture risk prediction ability.
Changes in bone mineral content after surgical treatment of morbid obesity. Surgical procedures to remedy morbid obesity are becoming more common. Although the surgeries often result in dramatic weight loss, it is possible that reduction in bone density might be a side effect. This could be due to the decreased weight since increased body mass index is a common finding in individuals with increased bone mineral density (BMD). And, it could be due to malabsorption problems of calcium or other vitamins and minerals resulting from the stomach bypass procedures. See: Metabolism 2004 Jul;53(7):918-21, Von Mach MA and others, PMID: 15254887. I won't go into all of the details on this study since it only involved 14 females and 5 males who had two different procedures. Nine patients underwent adjustable silicone gastric banding (ASGB) and 4 patients had the Roux-en Y gastric bypass (RYGB). The sample size is too small to make valid statistical correlations. But, since there was a dramatic reduction in bone mineral content in the RYGB group and none in the ASGB group, it behooves anyone who has the RYGB procedure done to pay close attention to their BMD via regular bone density testing. It may be possible that people having the RYGB procedure need to take higher and/or more frequent doses of vitamins and minerals to get adequate absorption to prevent osteoporosis or osteopenia. Or, there might be other reasons for the decreased BMD. Further studies are needed and hopefully will be done in the near future.