Seasonal changes of serum 25-hydroxyvitamin D and intact parathyroid hormone levels in a normal Japanese population

Abstract

We conducted an observational study in order to assess the prevalence of hypovitaminosis D and its seasonal changes, in the Tokai area (N35.3 E137.0), in 197 normal subjects in Japan. The mean serum 25-hydroxyvitamin D (25-OHD) level measured by direct radioimmunoassay (RIA) was lowest at the end of winter, and highest at the end of summer (15.1+/-7.1 ng/ml in March; 21.5+/-5.5 ng/ml in June; 31.6+/-5.6 ng/ml in September; 23.1+/-5.3 ng/ml in December; mean+/-SD). The prevalence of hypovitaminosis D (<20 ng/ml) was 86.7%, 33.4%, 1.0%, and 26.0% in March, June, September, and December, respectively. Mean plasma intact parathyroid hormone (iPTH) concentration was lowest at the end of summer and highest at the end of winter (28.2+/-9.3 pg/ml in March; 21.7+/-7.0 pg/ml in June; 19.8+/-6.9 pg/ml in September; and 25.7+/-9.2 pg/ml in December; mean+/-SD). Serum 25-OHD was inversely associated with iPTH (coefficient, -0.223; r=0.251; P<0.001). Serum 25-OHD levels were higher in men than in women. The serum 25-OHD level was positively associated with age, body weight, and body mass index, but not with body fat content. These results suggest a high prevalence of hypovitaminosis D associated with elevation of iPTH in Japan, in winter, even in a sunny area.

Hypovitaminosis D in Type 2 Diabetes Mellitus: Association with Microvascular Complications and Type of Treatment

“…1). As in previous studies on normal population [3,12,17], serum intact PTH levels were negatively correlated with serum 25-OHD concentrations in our populations (Fig. 2).…”

“…These findings suggest the decreased bioavailability of vitamin D3 due to its deposition in body fat component in obese population. In Japanese nonobese population, we have previously reported that not body fat content but BMI was positively associated with the increase of serum concentration of 25-OHD, suggesting the increase of the amount of non-fat tissue components such as skeletal muscles is related to the increase of 25-OHD [17]. As changes in body weight and body fat distribution are known to be closely related to insulin resistance and the occurrence of type 2 diabetes [26], these results suggest that the imbalance of body composition, for example the increase of visceral fat, in diabetes patients may contribute to the relationship between serum 25-OHD concentration and BMI.…”

Global vitamin D status and determinants of hypovitaminosis D

“…Overall, the vitamin D status in Japan is relatively better in the regions in South Asia and positively related to fish consumption [49][50][51]. Prevalence of hypovitaminosis D (<30 nmol/L) in women over 30 years old is only 10.3% [49] and in active elderly (25(OH)D <75 nmol/L) is below 5% [50].…”

Age, Sex, and Seasonal Variations in the Serum Vitamin D3 Levels in a Local Turkish Population

“…Similarly, Kashi et al 16 showed that both genders had 25-(OH)D deficiency in the summer and winter. On the other hand, a study by Ono et al 17 showed that the serum 25-(OH)D levels were higher in men than in women, but these differences could be related to how much skin was covered as well as their jobs.…”