# Dense sampling for mapping pituitary growth dynamics before, during, and after pregnancy

## TL;DR

This study tracks pituitary volume changes in pregnant women and finds significant anterior pituitary growth during pregnancy that returns to normal after childbirth.

## Contribution

The study provides the first detailed longitudinal mapping of anterior pituitary volume changes during human pregnancy using dense MRI sampling.

## Key findings

- Anterior pituitary volume decreased in the first trimester and increased sharply in the third trimester.
- Volume changes were reversible, returning to baseline by 3 months postpartum.
- Posterior pituitary volume remained stable throughout pregnancy and postpartum.

## Abstract

Pregnancy represents a period of profound endocrine activity and neural reorganization. While recent evidence highlights pituitary volume as a biomarker of endocrine dynamics during pregnancy, its precise trajectory (timing and relative magnitude of effect) across human pregnancy remains undescribed. Three healthy women (59 total observations) underwent T1‐weighted MRI before conception (5 baseline observations), during pregnancy (38 total observations, spanning gestational weeks 1–36), and up to 1 year postpartum (16 total observations). Anterior and posterior pituitary lobes were manually delineated at every visit. A longitudinal pipeline co‐registered each scan to all other intra‐subject scans, propagated their labels, and generated majority‐vote ensembles for objective and regularized volume estimates. Person‐centered z‐scores were computed, and generalized additive mixed models (GAMMs) with random intercepts estimated nonlinear volume trajectories. The anterior lobe followed a nonlinear trajectory, with gestational age explaining 73% of adjusted variance in anterior‐pituitary volume (edf = 7.59, F = 20.2, pbonf < 10−10). Specifically, volume exhibited a modest first trimester decrease (local fit minima: −0.9 SD at 10.6 weeks), followed by a steep rise into the 3rd trimester (local fit maxima: +1.8 SD at 34.1 weeks, or ~ 17.5% increase from 1st trimester minima, by volume), before returning to baseline near 3 months postpartum. Sensitivity analyses restricted to linear regression during early (−5 to 12 weeks) and late (12 to 40 weeks) windows replicated the observed non‐linear decreasing/increasing slopes (βearly = −0.09 SD/week, pearly = 0.036; βlate = 0.14 SD/week, plate < 10−10). In contrast, no significant volumetric changes in the posterior lobe were detected across the observation period (pnon‐linear = 0.79). In one of the first studies of its kind to leverage a dense sampling approach in multiple pregnant women, non‐linear analyses revealed rapid, reversible anterior pituitary hypertrophy across human pregnancy consistent with lactotrope expansion and heightened endocrine load.