To determine the effect of estrogen on vitamin D metabolism in pubertal girls, we studied 16 tall girls treated with a daily dose of 4-8 mg estradiol valerate to curtail excessive adult height. In all but one girl the plasma concentration of 1,25-dihydroxyvitamin D (1,25-(OH)2D) increased to values significantly higher than the corresponding pretreatment value (P less than 0.0005). The ratio of 24,25-dihydroxyvitamin D (24,25-(OH)2D) to 25-hydroxyvitamin D decreased in all girls (P less than 0.0005). The vitamin D binding protein (DBP) also increased significantly after estrogen (P less than 0.025), and there was a significant positive correlation between the plasma concentration of 1,25-(OH)2D and DBP (r = 0.66; P less than 0.0005). The free fraction of 1,25-(OH)2D remained unchanged after estrogen. It appears that estrogen treatment increases the plasma concentration of 1,25-(OH)2D. The effect might be explained by the concomitant increase in DBP and/or by estrogen stimulation of renal 1 alpha-hydroxylase.

Plasma concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, 24,25-dihydroxyvitamin D and vitamin D binding protein were determined in 87 serum samples from 46 Type 1 (insulin-dependent) diabetic children and adolescents at the various stages of puberty. The results were compared with data similarly obtained from healthy pubertal children. The diabetic patients had lower mean 1,25-dihydroxyvitamin D concentrations (p less than 0.05) and higher molar ratios of 24,25-dihydroxyvitamin D to 25-hydroxyvitamin D (p less than 0.05) than their healthy counter parts. In contrast to the reference group, the diabetic patients failed to attain the increase in 1,25-dihydroxyvitamin D normally seen during the pubertal stages of maximal growth velocity. The mean plasma levels of vitamin-D binding protein did not differ between the two groups, and a calculated 'free' 1,25-dihydroxyvitamin D value followed a pattern similar to that of total 1,25-dihydroxyvitamin D throughout puberty for both groups. The results suggest that the regulatory mechanisms of the vitamin D endocrine system are altered in diabetic children at puberty, resulting in a relative decrease in 1,25-dihydroxyvitamin D plasma concentration and increased 24,25-dihydroxyvitamin D levels.

Abstract. The serum concentrations of 25-dihydroxyvitamin D, 1,25-dihydroxyvitamin D, 24,25-dihydroxyvitamin D, vitamin D-binding protein, PTH and calcitonin were measured in three groups of elderly Norwegian subjects (age 70–96 years): active elderly living at home, warded geriatric patients not supplemented with vitamin D, and warded geriatric patients supplemented with a daily dose of 400 IU vitamin D2. The results were compared with the concentrations of vitamin D metabolites found in a group of young and middle-aged adults (age 22–59 years). Decreased serum concentrations of 25-dihydroxyvitamin D3 were found in all groups of elderly compared with younger adults. Active elderly living at home had higher concentrations of 25-dihydroxyvitamin D3 than geriatric ward patients. Supplementation of geriatric ward patients with 400 IU vitamin D2 resulted in an increase in the median serum 25-dihydroxyvitamin D concentration by about 30 nmol/l. Decreased median concentration of 1,25-dihydroxyvitamin D was found in geriatric ward patients not supplemented with vitamin D, indicating that this group is at risk of vitamin D deficiency. The active elderly living at home and the warded geriatric patients receiving vitamin D supplementation had normal median concentrations of 1,25-dihydroxyvitamin D, indicating that nephrogenous synthesis of 1,25-dihydroxyvitamin D is not generally impaired in the elderly, and that a moderate vitamin D supplementation may correct low 1,25-dihydroxyvitamin D levels owing to vitamin D deficiency. However, the serum concentrations of 1,25-dihydroxyvitamin D showed great individual variations. No significant differences were observed for vitamin D-binding protein, 'free-1,25-dihydroxyvitamin D' or PTH between the groups. The median serum concentrations of 24,25-dihydroxyvitamin D were significantly lower in all three groups of elderly compared with the younger adults.

Serum levels of vitamin D metabolites were determined in 11 patients treated for cystic acne with a four-month course of isotretinoin (Roaccutane). The levels were measured before treatment and after two months of medication. We found a significant fall in the level of 1,25-dihydroxyvitamin D (p less than 0.01) and a significant increase in the molar ratio of 24, 25-dihydroxyvitamin D to 25-hydroxyvitamin D (p less than 0.05). No significant changes were found for the vitamin D metabolites 25-hydroxyvitamin D or 24,25-dihydroxy-vitamin D, for serum calcium, phosphorus, alkaline phosphatase or parathyroid hormone. Our data indicate early changes in the metabolism of vitamin D in patients on retinoid treatment.