Effects of salmon calcitonin on the bone loss induced by ovariectomy

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Abstract
We present the results of a 12-month clinical study assessing the effects of synthetic salmon calcitonin (sCT) on a group of fertile white women who had undergone ovariectomy for uterine fibromatosis. The study was performed to verify whether CT can prevent the loss of bone mass and the changes in calcium-phosphorus metabolism associated with acute estrogen deficiency. The study consisted of an initial double-blind phase of 6 months, followed by a 6-month open period. Treated patients were given 100 MRC U of synthetic salmon CT injected i.m. in the morning, every other day, starting on the 7th day after the operation and continued for 12 months. Control patients received a placebo injection for the first 6 months; subsequently, they too were treated with sCT i.m. every other day for 6 months at the same dose as the 12 month-treated group. All patients received 500 mg of elementary calcium p.o., b.i.d. Bone mineral content (BMC) was measured at the extreme distal radius of the nondominant arm by a dual photon bone densitometer which utilizes two radio nuclides, 241 Am and 125 I, with energies of about 60 and 30 KeV. Biochemical parameters of the calcium-phosphorus metabolism were also measured. After 12 months of study, no significant changes of BMC were observed in the 12 months sCT treated group, while control patients, treated 6 months after the ovariectomy, showed a significant decrease in BMC values. Total hydroxyproline/ creatinine (OHPr/Cr) ratio, which increased after ovariectomy, returned to normal after the first month of sCT administration in the continuously treated group whereas it remained high in the control group up to the 6th month of observation, declining thereafter in coincidence with sCT treatment. The behavior of Bone GLA-protein (BGP), like that of the nondializable OHPr/Cr ratio, was substantially similar in both treated and control groups for the entire period of observation. These results show that prophylactic administration of salmon CT in ovariectomized women prevent estrogen deficiency-induced bone loss, inhibiting skeletal resorption and allowing osteogenesis to occur normally.