Miriam Antoinette Bredella MD, Presenter: Nothing to Disclose

Eleanor Lin, Abstract Co-Author: Nothing to Disclose

Danielle J Brick, Abstract Co-Author: Nothing to Disclose

Anu V Gerweck, Abstract Co-Author: Nothing to Disclose

Lindsey M Harrington, Abstract Co-Author: Nothing to Disclose

Martin Torriani MD, Abstract Co-Author: Nothing to Disclose

Bijoy J. Thomas MD, Abstract Co-Author: Nothing to Disclose

Anne Klibanski MD, Abstract Co-Author: Nothing to Disclose

Karen K. Miller MD, Abstract Co-Author: Nothing to Disclose

Recent studies suggest that abdominal adiposity is associated with low bone mineral density (BMD), high bone marrow (BM) fat, and low growth hormone (GH). Bone and fat cells arise from the same mesenchymal stem cells within BM, and GH is an important regulator of bone homeostasis. BMD is low in GH-deficient patients with pituitary disorders, and GH increases bone formation, with a decrease in BMD at 6 months, as bone expands, before mineralization, followed by an increase in BMD by 18 months. We hypothesized that 6 months of GH would increase bone formation and BM fat and decrease BMD in women with abdominal obesity.

79 premenopausal women with abdominal adiposity (mean age:36±7 y, mean BMI:35±5 kg/m2) participated in a 6-month, randomized, double-blind, placebo-controlled trial of GH administration. BM fat was determined by 1-H MRS and BMD by DXA. Abdominal fat depots and thigh muscle area were assessed by CT. P1NP, a marker of bone formation, CTX, a marker of bone resorption, and 25-OH vitamin D were assessed. Mean baseline and 6-month change were compared with ANOVA. Linear regression analysis was performed to determine predictors of bone turnover.

At baseline 32% of subjects were osteopenic (t-score <-1 and >-2.5) and 1 subject had osteoporosis (t-score <-2.5). GH increased IGF-1, P1NP, CTX, vitamin D, muscle mass, and BM fat, and decreased abdominal fat and BMD compared with placebo (p<0.05). 6-month change in P1NP correlated with 6-month change in CTX (r=0.34, p=0.04), consistent with the known coupling of bone formation and resorption. 6-month change in abdominal fat inversely predicted 6-month change in P1NP (r= -0.40, p=0.05), suggesting that subjects with the greatest loss of abdominal fat had greater increases in bone formation.

Low BMD is common in abdominally obese women. GH-induced loss of abdominal fat is associated with increased bone formation, consistent with a detrimental effect of abdominal fat on bone. GH replacement in abdominally obese women for 6 months increases bone formation and BM fat. The increase in BM fat content may reflect changes in energy demand from increased bone turnover.

Obesity does not always protect against osteoporosis. Loss of abdominal fat improves bone health. Replacement of GH for 6 months increases bone formation and bone marrow fat in abdominally obese women

Bredella, M, Lin, E, Brick, D, Gerweck, A, Harrington, L, Torriani, M, Thomas, B, Klibanski, A, Miller, K, Growth Hormone Administration Increases Bone Formation and Bone Marrow Fat in Premenopausal Women with Abdominal Obesity.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11008219.html