Age-dependent sex differences in calcium and phosphate homeostasis.

Background Sex differences in calcium and phosphate have been observed. We aimed to assess a relation with age. Methods We used laboratory values of serum calcium, phosphate and albumin from three different samples (years 2005, 2010 and 2014) using the hospital information system of Erasmus MC, Rotterdam. The samples were divided into 3 age groups: 1-17, 18-44 and ≥45 years. Sex differences in calcium and phosphate were analyzed using ANCOVA, adjusting for age and serum albumin. Furthermore, sex by age interactions were determined and we analyzed differences between age groups stratified by sex Results: In all 3 samples there was a significant sex*age interaction for serum calcium and phosphate, whose levels were significantly higher in women compared to men above 45 years. No sex differences in the younger age groups were found. In men, serum calcium and phosphate levels were highest in the youngest age group compared to age groups 18-44 and ≥45 years. In women, serum calcium levels were also significantly higher in the age group 1-17 and the age group ≥45 years compared to the 18-44 years age group. In women, serum phosphate was different between the three different age groups with highest level in the group 1-17 years and lowest in the group 18-44 years. Conclusion There are age dependent sex differences in serum calcium and phosphate. Furthermore, we found differences in serum calcium and phosphate between different age groups. Underlying mechanisms for these age- and sex differences are not yet fully elucidated.