Annual bone loss rate was estimated in a group of randomly selected 150 nonsurgical and nonosteoporotic early postmenopausal women, 42-56 years, with the use of the mathematical equation proposed by Christiansen et al. (OSTEOTREND-R) [1]. Fifty-six women were characterized as high turnover patients (estimated annual bone loss more than 2.7%). These high turnover patients were included in a double-blind, placebo-controlled clinical study. Patients were divided into two groups of 28 women each. The first group of patients received 100 IU of salmon calcitonin intranasally daily for 1 year and the second group intranasal spray of placebo daily. Blood and urine biochemical parameters as well as bone mineral content of the spine and proximal forearm were determined initially and at the end of 6 and 12 months. No other side effects were noted apart from discomfort of nasal mucosa in two patients (one in each group). The group of calcitonin-treated patients showed a dramatic decrease in bone loss rate as estimated with the use of biochemical bone markers at the end of 6 and 12 months (3.7% versus 0.8% and 0.0% at the end of 6 and 12 months, respectively, P < 0.001) whereas in the placebo group, bone loss rate remained unchanged (4.2% versus 4.1% and 4.3% at the end of 6 and 12 months, respectively). The calcitonin-treated patients showed a significant increase in bone mineral content of spine and proximal forearm (P < 0.001 at the end of 6 and 12 months, respectively). On the other hand, a significant decrease in all measurement sites appeared in the placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)