Occurrence of osteoporosis & factors determining bone mineral loss in young adults with Graves’ disease

BACKGROUND & OBJECTIVES: There is a paucity of data with conflicting reports regarding the extent and pattern of bone mineral (BM) loss in Graves’ disease (GD), especially in young adults. Also, interpretation of BM data in Indians is limited by use of T-score cut-offs derived from Caucasians. This study was aimed to evaluate the occurrence of osteoporosis in active treatment naive patients with GD and determine the factors predicting BM loss, using standard T-scores from Caucasians and compare with the cut-offs proposed by the Indian Council of Medical Research (ICMR) for diagnosing osteoporosis in Indians. METHODS: Patients with GD, >20 yr age without any history of use of anti-thyroid drugs, and normal controls without fracture history, drugs use or co-morbidities underwent BM density (BMD) assessment at lumbar spine, hip and forearm, thyroid function and calcium profile assessment. Women with menopause or premature ovarian insufficiency and men with androgen deficiency were excluded. RESULTS: Patients with GD (n=31) had significantly lower BMD at spine (1.01±0.10 vs. 1.13±0.16 g/cm(2)), hip (0.88±0.10 vs. 1.04±0.19 g/cm(2)) and forearm (0.46±0.04 vs. 0.59±0.09 g/cm(2)) compared with controls (n=30) (P<0.001). Nine (29%) and six (19.3%) patients with GD had osteoporosis as per T-score and ICMR criteria, respectively. None of GD patients had osteoporosis at hip or spine as per ICMR criteria. Serum T(3) had strongest inverse correlation with BMD at spine, hip and femur. Step-wise linear regression analysis after adjusting for age, BMI and vitamin D showed T(3) to be the best predictor of reduced BMD at spine, hip and forearm, followed by phosphate at forearm and 48 h I(131) uptake for spine BMD in GD. INTERPRETATION & CONCLUSIONS: Osteoporosis at hip or spine is not a major problem in GD and more commonly involves forearm. Diagnostic criterion developed from Caucasians tends to overdiagnose osteoporosis in Indians. T(3) elevation and phosphate are important predictors of BMD. Baseline I(131) uptake may have some role in predicting BMD.