Estrogen Deficiency as a Cause of Decreased 1-Alpha-Hydroxylase Activity

A 40-year-old woman with symptoms of vitamin D deficiency and estrogen deficiency, despite high levels of 25(OH)D (351.1 ng/mL) and normal parathormone (33.5 pg/mL), was found to have low estradiol levels (3.45 pg/mL). After initiating transdermal estrogen therapy, her parathormone levels decreased from 33.5 to 22.4 pg/mL. This case highlights the interdependence of vitamin D metabolism and sex steroids, particularly estrogen, which can affect the activity of the enzyme 1-alpha-hydroxylase (CYP27B1) responsible for converting 25(OH)D to its active form. The study suggests that in patients with high 25(OH)D levels, it is necessary to also measure parathormone and sex steroids like estrogen to accurately diagnose and treat vitamin D deficiency. The measurements were conducted using mass spectrometry for 25(OH)D and estradiol, and ELISA for parathormone.