Bone status in patients with hyperthyroidism: impact of the severity, duration, and etiology of hyperthyroidism on bone turnover markers and bone mineral density

ABSTRACT

Hyperthyroidism is accompanied by osteopenia or osteoporosis with higher incidence of fracture rates. There is paucity of data about the relation between the degree or duration of hyperthyroidism or its etiology and the resulting bone changes. The aim of the present work was to study bone status in patients with hyperthyroidism including biochemical markers of bone turnover and bone mineral density, and to elucidate the impact of severity, duration, and etiology of hyperthyroidism on biochemical markers of bone turnover and bone mineral density. Subjects and Thirty-six male patients with hyperthyroidism, 21 with Graves' disease and 15 with toxic multinodular goiter, with an age ranging from 23 to 65 years and a mean of 43 +/- 10 years, were included, together with 10 healthy men with matched age as a control group. In addition to full clinical examination, patients were subjected to radioisotope scanning and uptake of the thyroid gland with Tc 99,and DEXA scanning of the lower half of the left radius. Laboratory work up included serum free T3, free T4, TSH. Special assays done for patients and controls included serum total and B-ALP, serum OC, serum calcium, serum phosphorus urinary calcium, urinary DXP cross-links, urinary creatinine and calculated urinary DXP/urinary creatinine ratio. Biochemical markers of bone turnover were significantly higher in patients with Graves' disease compared to controls. Serum B-ALP was 9,5 +/- 5.6 KAU/I versus 2.2 +/- 0.8 KAU/I [P=0.00], serum OC was12.7 +/- 5 ng/dl versus 6.6 +/- 1.6 ng/dl [P=0.00], urinary calcium was 22.6 +/- 7.5 mg/dl versus15.5 +/- 5.1 mg/dl [P<0.05], and urinary DXP/urinary creatinine ratio was 12.6 +/- 5.5 versus 6.3 +/- 1.8 [P=0.00]. Biochemical markers of bone turnover were significantly higher in patients with toxic multinodular goiter compared to controls. Serum B-ALP was 4.3 +/- 2.6 KAU/I versus 2.2 +/- 0.8 KAU/I [P<0.05], serum OC was11.5 +/- 6.1 ng/dl versus 6.6 +/- 1.6 ng/dl [P<0.05], urinary calcium was 19.2 +/- 5 mg/dl versus15.5 +/- 5.1 mg/dl [P<0.05], and urinary DXP/urinary creatinine ratio was 13.5 +/- 7 versus 6.3 +/- 1.8 [P<0.05]. There was nonsignificant difference in the biochemical markers of turnover in patients with Graves' disease compared to those with toxic multinodualr goiter. Serum OC was 12.7 +/- 5 ng/d versus11.5 +/- 6.1 ng/dl, urinary calcium was 22.6 +/- 7.5 mg/dl versus 19.2 +/- 5 mg/dl, and urinary DXP/urinary creatinine ratio was 12.6 +/- 5.5 versus 13.5 +/- 7. However, serum B-ALP was higher in patients with Graves1 disease compared to those with multinodular goiter [9.5=/=5.6 KAU/I versus4.3 +/- 2.6 KAU/I [P< 0.05]. The Z -score at the lower half of the left radius in patients with Graves' disease [-1.7 +/- 0.5] was not significantly different from those with toxic multinodular goiter [-1.6 +/- 6]. Correlation between free T3 and biochemical markers of bone turnover revealed a significant positive correlation with all studied parameters B-ALP [n= 0,37, P<0.05], serum OC [r= 0.62, P<0.05], urinary calcium [r=0.46, P<0.05], and urinary DXP/urinary creatinine ratio [r=0.52, P<0.05]. Correlation between free T4 and bone turnover markers revealed a significant positive correlation with B-ALP [r=0.43, P<0.05], serum OC [r=0.65, P<0.05], urinary calcium [r= 0.61, P<0.05], and urinary DXP/ urinary creatinine ratio [r=0.49, P< 0.05]. The duration of the thyrotoxic state did not correlate with the assessed bone turnover markers. However, the duration of the thyrotoxic state correlated significantly with the Z-score of the studied patients [r =0.68, P< 0.05]. The Z-score of the studied patients did not correlate with the free T3 and freeT4. Conclusions: It is concluded that men with hyperthyroidism have significant bone loss with higher biochemical markers of bone turnover. The severity of hyperthyroidism is directly related to the derangement of biochemical markers of bone turnover. Duration of the thyrotoxic state is related to the degree of bone loss. The etiology of the thyrotoxic state is not related to the degree of derangement in bone turnover markers or to the degree of bone loss