Original Article Hypovitaminosis D and Bone Mineral Metabolism and Bone Density in Hyperthyroidism Dinesh Kumar Dhanwal, * ,1,2 Narayana Kochupillai, 3 Nandita Gupta, 4 Cyrus Cooper, 1,5 and Elaine M. Dennison 1 1 MRC Epidemiology Resource Centre, Southampton General Hospital, University of Southampton, Southampton, UK; 2 Maulana Azad Medical College, New Delhi, India; 3 SRM Medical College, Kattankulathur, India; 4 All India Institute of Medical Sciences, New Delhi, India; and 5 Botnar Research Centre, Institute of Musculoskeletal Sciences, University of Oxford, Oxford, UK Abstract Little is known about the impact of concomitant vitamin D deficiency on bone mineral density in hyperthyroid- ism. Therefore, we evaluated bone mineral measures in vitamin Dedeficient and sufficient patients with hyperthy- roidism. Thirty newly diagnosed consecutive patients with hyperthyroidism were included. Blood samples were used for measurement of calcium, phosphate, alkaline phosphatase, 25-hydroxy vitamin D [25(OH) D], and parathyroid hormone (PTH). Bone mineral density (BMD) was measured at the hip, spine, and forearm. The patients were di- vided into vitamin Dedeficient (!25 nmol/L) and vitamin Desufficient groups (25 nmol/L). Eight (26.6%) pa- tients had 25(OH) D levels less than 25 nmol/L, with mean  standard deviation (SD) level of 16.5  3.2 (vitamin Dedeficient group 1), and the remainder had a mean  SD of 46.0  13.5 nmol/L (vitamin Desufficient group 2). Serum-intact PTH levels were significantly higher in group 1 compared with those in group 2 (31.2  16.3 vs 18.0  13.1 pg/mL; p 5 0.041). In the vitamin Dedeficient group, the mean BMD T-scores were in the osteoporotic range at hip and forearm (2.65  1.13 and 3.04  1.3) and in the osteopenia range at lumbar spine (1.83  1.71). However, in vitamin Desufficient group, the mean BMD T-scores were in the osteopenia range (1.64  1.0, 1.27  1.6, and 1.60  0.7) at hip, forearm, and lumbar spine, respectively. The mean BMD Z-scores were also significantly lower in vitamin Dedeficient group compared with those in vitamin Desufficient group. Finally, BMD values (gm/cm 2 ) at the hip and forearm were significantly lower in the vitamin Dedeficient group compared with those in the vitamin Desufficient group. In conclusion, hyperthyroid patients with concomitant vitamin D deficiency had lower BMD compared with vitamin Desufficient patients. Key Words: Bone mineral density; hyperthyroidism; hypovitaminosis D; thyrotoxicosis; vitamin D deficiency. Introduction Hyperthyroidism is a known cause of secondary osteopo- rosis (1). Thyroid hormones have a direct catabolic effect on bone mineral homeostasis, leading to increased bone min- eral resorption and calcium loss through the kidneys (2,3). Several novel clinical features of thyrotoxicosis, including hyperpigmentation of skin and malabsorption, have been reported from India during late stages of natural history of Graves’ disease (4,5). Increased skin pigmentation, malab- sorption, and related vitamin D deficiency, coupled with ex- cessive urinary calcium loss, caused by thyrotoxicosis, may well be responsible for causing significant abnormalities in bone mineral homeostasis in these thyrotoxic patients. Nega- tive calcium balance because of a catabolically induced increase in bone resorption may also be operative in thyro- toxic patients. Vitamin D deficiency or insufficiency is common in both rural and urban India because of skin pigmentation and Received 04/14/10; Revised 05/21/10; Accepted 05/23/10. *Address correspondence to: Dinesh K. Dhanwal, DM, Deapart- ment of Medicine (Endocrinology Division), Maulana Azad Medical College, New Delhi, India 110002. E-mail: dineshdhanwal@ hotmail.com 462 Journal of Clinical Densitometry: Assessment of Skeletal Health, vol. 13, no. 4, 462e466, 2010 Ó Copyright 2010 by The International Society for Clinical Densitometry 1094-6950/13:462e466/$36.00 DOI: 10.1016/j.jocd.2010.05.008