A comparative study of hormonal contraceptive use and vitamin D levels at Gondar Town 2023

Vitamin D deficiency is an emerging public health problem globally, with devastating health consequences. Some studies suggest that exogenous sex hormones, found in hormonal contraceptives, may enhance vitamin D levels. However, the reasons for this association are not fully understood, as women using hormonal contraception may have different lifestyle habits affecting their vitamin D status. Therefore, this study seeks to explore the relationship between hormonal contraceptive use and vitamin D levels. A Facility based comparative cross-sectional study was conducted in Gondar town from February to April 2023, involving a total of 162 women using three types of hormonal contraceptives (Norplant, DMPA, and COC) and 162 age and BMI-matched non-users as controls in a 1:1 ratio. Participants were selected using systematic random sampling. A semi-structured questionnaire was used to collected data regarding the socio-demographic, economic, obstetric, lifestyle, and clinical information. 5 milliliters of blood samples were collected from each participant for Laboratory analysis of serum vitamin D, calcium, and alkaline phosphates using a Beckman Coulter chemistry analyzer. Independent t-tests, ANOVA with post hoc Bonferroni test was used to compare statistics between the two groups, and logistic regression models to identify factors associated with Vitamin D deficiency. The mean serum Vitamin D levels of Norplant, DMPA, and COC users were 24.08 (± 5.17), 24.83 (± 5.52), and 31.90 (± 6.94) respectively; whereas control group has mean Vitamin D level of 22.00 (± 7.97). On the current study the prevalence of Vitamin D deficiency (< 20 ng/ml) among hormonal contraceptive users was found to be 21.6% (35/162), whereas 48.14% (78/162) of non-user controls had vitamin D deficiency. The odds of having Vitamin D deficiency was higher among participants who attained higher education, who never eat fish and have never been used vitamin D Supplements. However, the use of combined oral contraceptives (COC) shown to reduce the odd of having vitamin D deficiency by 90%. Similarly, individuals with normal and hypercalcemia state shown to have lower odd of having Vitamin D deficiency. Users of combined oral contraceptives (COC) had significantly higher mean serum Vitamin D levels compared to users of Norplant and DMPA, as well as non-users. The prevalence of Vitamin D deficiency was lower among COC users compared to non-users, highlighting a potential protective effect of COC use against Vitamin D deficiency.