Association of 25-hydroxyvitamin D with sex hormones and body composition in Chinese older adults.

The prevalence of vitamin D insufficiency or deficiency was very high among older Chinese adults, affecting 87.4% of males and 91.8% of females.

• Study enrolled 2472 older adults (1406 males; 1066 females) aged 60 years or older
• Participants underwent routine health examinations at the Chinese PLA General Hospital in 2018 and 2019
• 87.4% (1229/1406) of males had insufficient/deficient vitamin D
• 91.8% (979/1066) of females had insufficient/deficient vitamin D

In males, a 10 ng/ml decrease in 25-(OH)D was associated with a significant decline in testosterone levels and increased risk of hypogonadism before adjustment for age and BMI.

• A 10 ng/ml decrease in 25-(OH)D was associated with a -0.95 (-1.46, -0.45) nmol/L change in testosterone levels
• A 10 ng/ml decrease in 25-(OH)D was associated with a 26% higher risk of hypogonadism (defined as total testosterone <12 nmol/L)
• These associations disappeared after adjusting for age and BMI
• This suggests the vitamin D-testosterone relationship may be mediated by BMI/adiposity

By 25-(OH)D stratification from sufficiency to deficiency, males showed increasing trends in BMI, waist circumference, body fat percentage, muscle mass, and basal metabolic rate, along with decreasing trends in testosterone.

• Increasing trends observed in BMI, waist circumference (WC), body fat percentage, muscle mass, and basic metabolic rate (all P<0.05)
• Increasing trends also observed in smoking rate, triglycerides (TG), parathyroid hormone (PTH), and prolactin (PRL)
• Decreasing trends observed in albumin (Alb), serum calcium (Ca), HDL-C, serum creatinine (Cr), AST, and testosterone (all P<0.05)

Females showed similar trends to males with decreasing 25-(OH)D, with additional decreases in hemoglobin, luteinizing hormone, and follicle-stimulating hormone.

• Females exhibited increasing trends in BMI, waist circumference, body fat percentage, muscle mass, and basal metabolic rate with decreasing 25-(OH)D
• Additional decreasing trends were observed in hemoglobin (Hb), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) compared to males
• All trends were statistically significant (P<0.05)

For every 10 ng/ml decrease in 25-(OH)D, body fat percentage, muscle mass, and basal metabolic rate increased in both older males and females, but after adjusting for confounding factors only body fat percentage remained significant in older males.

• After adjusting for confounding factors, body fat percentage increased by 0.30 (0.00, 0.59) % in older males per 10 ng/ml decrease in 25-(OH)D
• The associations of 25-(OH)D with muscle mass and basal metabolic rate were no longer significant after adjustment
• The association with body fat percentage was not retained in females after full adjustment
• Cross-sectional design was used with multiple linear regression and logistic regression analyses