Peripartum Fluoxetine Reduces Maternal Trabecular Bone After Weaning and Elevates Mammary Gland Serotonin and PTHrP.

Selective serotonin reuptake inhibitors (SSRIs) have been linked to osteopenia and fracture risk; however, their long-term impact on bone health is not well understood. SSRIs are widely prescribed to pregnant and breastfeeding women who might be at particular risk of bone pathology because lactation is associated with considerable maternal bone loss. We used microCT and molecular approaches to test whether the SSRI fluoxetine, administered to C57BL/6 mice from conception through the end of lactation, causes persistent maternal bone loss. We found that peripartum fluoxetine increases serum calcium and reduces circulating markers of bone formation during lactation but does not affect osteoclastic resorption. Peripartum fluoxetine exposure also enhances mammary gland endocrine function during lactation by increasing synthesis of serotonin and PTHrP, a hormone that liberates calcium for milk synthesis and reduces bone mineral volume. Peripartum fluoxetine exposure reduces the trabecular bone volume fraction at 3 months after weaning. These findings raise new questions about the long-term consequences of peripartum SSRI use on maternal health.