[Bone density and mineral metabolism in calcitonin-deficiency patients]

Calcitonin is a hormone secreted by thyroid C-cells. Its primary effect seems to be a direct inhibition of bone degradation, but the physiological function of calcitonin in humans is still uncertain. The role of this hormone in the development of osteoporosis is unknown, but few authors have shown bone mass reduction in thyroidectomy patients.

To investigate the influence of calcitonin deficiency on bone turnover, 9 males (age 31 to 66 years) submitted to total thyroidectomy in 1996 for non-toxic goitre have been studied. These patients received thyroxine treatment at individual dose but never with suppressed TSH levels. Moreover 8 sex-, age- and Body Mass Index-matched normal subjects have also been studied as control group.

Calcitonin was undetectable in thyroidectomized patients, while the mean value was 7.1+/-3.2 pg/ml in the control group. At bone ultrasonography 50% of patients showed osteopenia, while only 1 subject showed osteopenia in the control group. The mean calcium serum level of patients was significant lower than in the control group (p<0.001). Calcium urinary level was increased in patients than controls. PTH serum levels were statistically decreased (p<0.001) in patients more than in controls. Osteocalcin showed a significantly (p<0.05) lower bone formation in patients than in controls, while the markers of resorption, deoxypyridinoline and N-terminal telopeptide of type I collagen, suggested an increased bone turnover in calcitonin-deficiency patients.

The results of this study show that the chronic lack of calcitonin in total thyroidectomized patients may play a role in increased bone degradation and osteopenia with a higher risk of bone fracture.