Influence of denosumab on bone mineral density in a severe case of pregnancy-associated osteoporosis

Pregnancy and lactation-associated osteoporosis (PLO) with predominantly subsequent vertebral fracture is a rare but severe disease with an estimated incidence of 0.4 in 100,000. In the past, patients with PLO have been predominantly treated with oral and i.v. bisphosphonates to reduce subsequent fracture risk. Hereby, the use of bisphosphonates in premenopausal women is controversial, as bisphosphonates know to persist in bone for many years and can be exposed and circulate in maternal serum and subsequently pass the placenta barrier and may have a detrimental effect on fetal bone health. Here we report the effects of denosumab on the bone mineral density (BMD) and subsequent fracture risk in PLO. In this case presentation, denosumab was administered postpartum with 3000 IE vitamin D and 1000 mg of calcium daily in a patient with PLO and vertebral fracture of L1 and L4. After 18 months of treatment with denosumab, we could demonstrate a clinical significant increase of BMD at the lumbar spine, femoral neck, and total hip of 32.2%, 13.0%, and 11.5% respectively with no further subsequent fractures. As the patient had regular menstrual cycles and considered a further pregnancy, denosumab treatment was terminated and soon a second pregnancy occurred. After the second pregnancy, BMD decreased at the lumbar spine, femur neck, and total hip by −8.8%, −6.9%, and −7.0% respectively compared to the maximum values during treatment with denosumab, but was still significantly higher compared to baseline levels with no further fractures.