Bone mineral density in patients receiving suppressive doses of thyroxine for thyroid carcinoma.

AIMS: Studies of the effect of thyroxine therapy on skeletal integrity have given conflicting results; the reductions in bone mass reported by some have prompted recommendations that the prescribed replacement doses of thyroxine should be reduced. We have examined bone mineral density in a group of patients with differentiated thyroid carcinoma receiving high doses of thyroxine to suppress thyroid stimulating hormone (TSH). METHODS: The 44 patients (6 male, 38 female) had a median age of 49 years (range 27-75) with median duration of thyroxine therapy of 9.0 years (range 3 to 42) and mean dose of thyroxine 0.167 mg/day (range 0.125-0.3). TSH levels were chronically suppressed in 39 subjects. Bone mineral density (BMD) was measured by dual energy x-ray absorptiometry (DEXA) in all subjects at the femoral neck and lumbar spine and compared with previously established local reference ranges. RESULTS: There was no reduction in bone mineral density in the thyroxine treated group compared with the local reference population at both lumbar spine and femoral neck, and no correlation with duration of therapy. CONCLUSIONS: These negative findings, that thyroxine in suppressive doses does not significantly reduce bone mineral density in New Zealand patients suggest that thyroxine therapy alone is not a major risk factor for the development of osteoporosis.

Factors affecting bone mineral density in high school girls.

OBJECTIVES: first to establish a local normal range for hip and spine bone density in the teenage years. Secondly to determine what factors might affect bone mineral density at this age. METHODS: bone mineral density (DPX absorptiometer) at the hip and spine in a cohort of 138 high school girls; mean age 16.4 yr (SD 0.34). Anthropometric factors, calcium intake, physical activity and other lifestyle and medical data were documented in each subject. RESULTS: in this group of 16 year old schoolgirls mean bone mineral density at the hip, 1.01 (0.13) was not significantly different from 20-25 year old New Zealand females, but bone mineral density at lumbar spine, 1.17 (0.12), was significantly lower. Positive correlations of bone mineral density with weight, height, physical activity and calcium intake were demonstrated. Weight was clearly the best predictor of bone mineral density variability. Calcium intake and physical activity showed no predictive value at the spine but contributed significantly at all regions of the femur and particularly at the trochanter. CONCLUSIONS: it appears that peak bone mass can be modified by nutrition and exercise. Adolescents should be encouraged into regular exercise programmes and to maintain adequate body mass and calcium intakes.