Possible effect of calcitonin deficiency on bone mass after subtotal thyroidectomy

Bone mass is purportedly reduced by an excess of endogenous or exogenous thyroid hormone or perhaps by calcitonin deficiency. Patients who have undergone thyroidectomy could be subject to all of these effects. In the present study we tried to demonstrate, whether lack of calcitonin following thyroidectomy has a significant influence on bone density. We measured thyroid hormone levels, TSH and calcitonin and assessed the bone mass in the hip and lumbar spine of 55 patients (32 f, 23 m), who had undergone a subtotal thyroidectomy between 1938 and 1996 on the reason of a non-toxic goitre. TSH levels were suppressed in 16 patients. Serum concentration of total calcium, intact PTH, osteocalcin were normal in all subjects. The mean fasting calcitonin level was in the patient group 2.09 +/- 0.7 pg/ml and in the control group, age matched healthy volunteers, 2.8 +/- 1.2 pg/ml. However, the serum level of calcitonin was not significantly lower than in the control group. 43 patients had an osteopenia or osteoporosis. The interpretation of the results in this study is hampered by the fact, that in women results may be influenced by involutional osteoporosis. Therefore we focus on the potential for osteoporosis among the 23 men. The results of our study indicates, that there is a significant reduction in bone mass in male after thyroidectomy, no matter whether T4 therapy is given or not, and whether TSH is suppressed or in a normal range.