PTH increasing with BMI associated with cortical bone density

Uygur Meliha Melin

doi:10.1530/endoabs.90.P314

Objective: The goal in this study was to evaluate serum parathormone (PTH) and 25-hydroxy-vitamin D (25OHD), calcium levels and bone mineral density (BMD) in patients with obesity and determine the relationship between biochemical bone parameters, body mass index (BMI) and trabecular/cortical BMD over a wide range of body weights.

Methods: We examined 337 women (mean age 41.35 years old; BMI 45.47 kg/m²) who were classified into three categories of BMI 30-40, 40-50, 50-60 including obese-class I-II (BMI 30-34.9 and BMI 35-39.9) and obese-class III (BMI>40). Bone mineral density (g/cm²), trabecular, and cortical bone components were measured by dual energy X-Ray absorptiometry; and calcium, PTH, and 25OHD were analyzed.

Results: Mean age was similar among the BMI groups. PTH levels were significantly higher in BMI group 2 and 3 than group 1 (P=0.003), though 25OHD and calcium levels were not significantly different among the groups (P=0.82,0.052; respectively). Postmenopausal women with obesity had lower cortical BMD than premenopausal women (P<0.001). There was a negative correlation between PTH levels and cortical BMD (P=0.001). Menopause status, BMI and PTH but not age were the predictors for cortical BMD (R2= 0.346, P<0.001) (Table-1).

Table 1: Regression analysis prediction cortical bone mineral content in total cohort
	Beta coefficient (B.C.)	Sig.	95% confident interval for B.C.
			Lower Bound	Upper Bound
Menopause Status	-0.264	<0.001	<0.104	-0.043
PTH	-0.264	<0.001	<0.104	-0.043
BMI	0.126	<0.027	<0.000	0.006

Conclusion: Increased PTH levels were seen in patients with higher BMI without a significant difference in calcium and 25OHD levels. PTH was negatively associated with cortical BMD. Whether or not PTH levels in obesity influences fracture risk needs to be further explored[1, 2].

Reference: 1. Aloia JF, Feuerman M, Yeh JK. Reference range for serum parathyroid hormone. Endocr Pract. 2006;12(2):137-44. Epub 2006/05/13. doi: 10.4158/ep.12.2.137. PubMed PMID: 16690460; PubMed Central PMCID: PMCPMC1482827.

2. Sukumar D, Schlussel Y, Riedt CS, Gordon C, Stahl T, Shapses SA. Obesity alters cortical and trabecular bone density and geometry in women. Osteoporos Int. 2011;22(2):635-45. Epub 2010/06/10. doi: 10.1007/s00198-010-1305-3. PubMed PMID: 20533027; PubMed Central PMCID: PMCPMC2994953.

Endocrine Abstracts

P314