Pregnancy and lactation associated osteoporosis (PLO) is a rare presentation of early-onset osteoporosis characterized by low trauma, spontaneous fractures during late pregnancy/lactation. Herein, we report areal BMD (aBMD) by DXA and volumetric BMD (vBMD), microarchitecture and strength at the distal radius and tibia by HR-pQCT in 59 women with PLO - in comparison to both healthy premenopausal Controls (n = 28) and premenopausal women with idiopathic osteoporotic fractures not associated with pregnancy/lactation (Non-PLO IOP;n = 50). Women with PLO (aged 34 ± 6 yrs) had a more severe clinical presentation than Non-PLO IOP: 80% had vertebral and 92% had multiple fractures (P<.001). They had lower DXA aBMD at all sites vs Controls (all P<.001) and non-PLO IOP (all P<.05). By HR-pQCT, PLO had deficits in all radial/tibial density and most microarchitecture parameters, and lower bone strength than Controls (all P<.001). Compared to non-PLO IOP, PLO had lower total and trabecular density at radius and tibia (all P≤.01) and significant deficits in trabecular microstructure and cortical thickness at the radius only. We studied PLO subgroups with clinical factors potentially related to bone physiology: Within PLO, women with vertebral fractures had lower spine aBMD and higher tibial cortical porosity but were otherwise structurally similar to the nonvertebral group. Those with prior heparin exposure had larger bone size and trabecular area, and those with renal stones had smaller bone size and lower 1/3radius aBMD. We also compared groups based on postpartum timing: Recent PLO (n = 25) evaluated ≤12 M postpartum, before expected recovery of pregnancy/lactation bone loss, had significantly lower aBMD than Distant PLO (n = 34) evaluated >12 M postpartum. However, radial/tibial HR-pQCT measures did not differ, suggesting pre-existing and/or persistent structural deficits. This structural study increases our mechanistic understanding of the severe bone fragility presentation that characterizes PLO and also highlights areas of potential mechanistic heterogeneity that require additional investigation.
Keywords: Bone microstructure; Bone strength; Early onset osteoporosis; Hr-pqct; Low-trauma fracture; Pregnancy and lactation associated osteoporosis.
Pregnancy and lactation associated osteoporosis (PLO) is a rare and often severe presentation of early-onset osteoporosis characterized by low trauma, spontaneous fractures during late pregnancy or lactation. Most women identified as having PLO sustain multiple fractures - most commonly spine fractures - that occur during lactation, at an average of 2 months postpartum. This study aimed to investigate bone structure in PLO in 59 women with PLO who were compared to two control groups: 28 healthy premenopausal women (Controls) and 50 premenopausal women with idiopathic osteoporotic fractures not associated with pregnancy/lactation (Non-PLO IOP). Using DXA to assess bone mineral density (BMD) at the spine, hip and forearm and high resolution peripheral quantitative computed tomography (HR-pQCT) to assess 3 -dimensional bone structure at the radius and tibia, we documented significantly lower BMD and substantial bone structure deficits in PLO in comparison to both control groups. We also documented structural differences in PLO subgroups based on presence of vertebral fractures, renal stones, and heparin exposure, as well as in subgroups based on postpartum timing. This structural study increases our mechanistic understanding of the severe bone fragility presentation that characterizes PLO.
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