Effect of vitamin D intake on seasonal variations in parathyroid hormone secretion in postmenopausal women

Abstract

Abstract Vitamin D intake should be sufficient to maintain calcium absorption and prevent increased parathyroid secretion throughout the year. To determine the level of intake that achieved the latter in elderly women, we studied the interrelations among vitamin D intake, serum 25-hydroxyvitamin D (25(OH)D) levels, and parathyroid hormone concentrations in a cross-sectional study of 333 healthy, white, postmenopausal women with low median calcium (408 mg a day) and vitamin D (112 IU a day) intakes who lived in Massachusetts. The overall inverse relation between serum parathyroid hormone and 25(OH)D levels was found to be dependent on vitamin D intake. In women whose estimated intake of vitamin D was ≤220 IU a day, the mean (±SD) serum parathyroid hormone values were lowest in those studied between August and October (30±11 ng per liter; n = 72) and highest in those studied between March and May (37±16 ng per liter; n = 54); the respective serum 25(OH)D levels were 93±32 and 63±21 nmol per liter. At vitami...