A 5‐year controlled randomized study of prevention of postmenopausal trabecular bone loss with nasal salmon calcitonin and calcium

Abstract. The aim of this paper was to evaluate the long‐term (5 years) efficacy of nasal salmon calcitonin in prevention of trabecular postmenopausal bone loss, which was a follow‐up of a previously published study (3 years); a randomized, controlled group comparison. One hundred healthy postmenopausal women were randomly chosen from those (186) having completed the 3 year protocol. The 100 women were allocated to an additional 2 year period (total of 5 years) of treatment with either 500 mg d‐1, 5 days week‐1 of calcium or the same amount of calcium plus 50 IU d‐1, 5 days per week of nasal salmon calcitonin, 87 (87%) women complied with the protocol throughout. The main outcome measures were the bone mineral density of the lumbar spine (1‐BMD) (DPA) and biochemical parameters reflecting bone turnover (serum alkaline phosphatases, urinary calcium/creatinine and hydroxyproline/creatinine ratios). The women receiving calcium alone presented a significant decrease in 1‐BMD after 6 months [– 1·6 (0·5)%] [mean(SEM)] (P < 0·01) and this decrease remained significant after 36 months [– 6·1(0·8)%] (P < 0·01) and until the end of the trial [– 6·6(1·0)% at t60] (P < 0·01). In women receiving calcium and calcitonin, 1‐BMD significantly increased after 36 months [+ 2(0·7%] (P < 0·01) and 42 months [+ 2·5(0·7)%] (P < 0·01) and was unchanged at the other times of investigation [+ 1·1(1·1)% at t60] (NS). The evolution of BMD in the two groups was highly significantly different (P < 0·001) since the sixth month of the study and remained so until the end of the study. No differences were observed in the biochemical parameters reflecting bone turnover. Nasal administration of salmon calcitonin, using a low‐dose (50 IU d‐1), intermittent (5 days week‐1) regimen, may totally prevent postmenopausal bone loss, at the level of the lumbar spine, for at least 5 years, if the treatment is continued for this duration. It is not clear whether the results observed during the fourth and fifth years are fully attributable to calcitonin or if calcium by itself plays also a protective role against trabecular bone loss.