Endocrine Abstracts

We present the case of a 35-year-old woman who was well until pregnancy 4y previously in Israel. Her antenatal course was uncomplicated. She breastfed postpartum and a few months into this she experienced acute back pain on reaching for a nappy. MRI demonstrated six vertebral fractures. DEXA scan confirmed osteoporosis (lumbar T-score −4.3, hip T-score −3.3). She received a single dose of denosumab. She moved to the UK 2y later and was referred to our Endocrine Bone Clinic. Repeat DEXA scan showed improving bone mineral density (BMD, lumbar T-score −3.6), with raised Bone-ALP (23.7iu/l, NR6.5-14.9) and normal uNTx (18 nmolBCE/mmolCr, NR5-65), suggesting ongoing new bone formation. Osteoporosis risk factors were identified as previous low BMI, ex-smoker, previous vitamin D deficiency, previous SSRI exposure, family history of osteoporosis and breastfeeding 18 months postpartum. Additional secondary causes were excluded. Given her young age and improving BMD, we have currently advised calcium, vitamin D and exercise, as any anti-resorptive therapy may stunt her continued recovery. Teriparatide is an option to consider if improvement plateaus. It is likely that her pre-pregnancy BMD was suboptimal given the additional risk factors above. Therefore, this case highlights pregnancy/lactation-induced BMD deterioration adding to this risk and resulting in multiple fractures. Calcium homeostasis is significantly altered during pregnancy and lactation. Current data suggest small BMD increases at cortical but decreases at trabecular sites like the spine. Subsequent lactation requires a large calcium provision to the baby, which is provided predominantly from maternal bone. In addition, hyperprolactintaemia-induced oestrogen suppression results in further bone loss. Combined, lactation can induce up to 10% BMD loss. This case illustrates the serious consequences of bone loss during pregnancy and lactation especially when starting from a suboptimal density, highlighting the need to consider cautioning patients with reduced bone density regarding future lactation.