Oral contraceptive use is associated with smaller hypothalamic and pituitary gland volumes in healthy women: A structural MRI study

The effects of hormonal contraceptives on structural features of the hypothalamus and pituitary are incompletely understood. One prior study reported microstructural changes in the hypothalamus with oral contraceptive pill (OCP) use. However, effects on hypothalamic volume have not been reported. One prior study reported volumetric changes in the pituitary. However, this study was limited by including participants evaluated for neurological symptoms. We sought to determine if OCP use is associated with alteration of hypothalamic or pituitary volume. High-resolution 3T MRI was performed for a prospective cohort of 50 healthy women from 2016 to 2018, which comprised 21 OCP users (age, 19–29) and 29 naturally cycling women (age, 18–36). Participants were excluded if they were pregnant or had significant medical conditions including neurological, psychiatric, and endocrine disorders. After confirming reliability of the image analysis techniques, 5 raters independently performed manual segmentation of the hypothalamus and semi-automated intensity threshold-based segmentation of the pituitary using ITK-SNAP. Total intracranial volume was estimated using FreeSurfer. A general linear model tested the association of OCP use with hypothalamic and pituitary volumes. Hypothalamic (B = -81.2 ± 24.9, p = 0.002) and pituitary (B = -81.2 ± 38.7, p = 0.04) volumes in OCP users were smaller than in naturally cycling women. These findings may be related to interference with known trophic effects of sex hormones and suggest a structural correlate of central OCP effects.