ENDOCRINOLOGY IN PREGNANCY: Bone metabolic changes during pregnancy: a period of vulnerability to osteoporosis and fracture

Abstract

Changes in bone density and bone markers suggest that pregnancy is associated with deterioration of bone mass in the mother. The metabolism of calcium resets to allow for the needs imposed by the building of the fetal skeleton. The fetus contributes to the process through the output of regulators from the placenta. Understanding of the whole process is limited, but some changes are unambiguous. There is an increase in the circulating levels of vitamin D, but its functional impact is unclear. Fetal parathyroid hormone (PTH) and PTH-related peptide (PTHrp) play an indirect role through support of a calcium gradient that creates hypercalcemia in the fetus. Placental GH, which increases up to the end of pregnancy, may exert some anabolic effects, either directly or through the regulation of the IGF1 production. Other key regulators of bone metabolism, such as estrogens or prolactin, are elevated during pregnancy, but their role is uncertain. An increase in the ratio of receptor activator of nuclear factor kappa B ligand (RANKL) to osteoprotegerin (OPG) acts as an additional pro-resorbing factor in bone. The increase in bone resorption may lead to osteoporosis and fragility fracture, which have been diagnosed, although rarely. However, the condition is transitory as long-term studies do not link the number of pregnancies with osteoporosis. Prevention is limited by the lack of identifiable risk factors. When fractures are diagnosed, rest, analgesics, or, when indicated, orthopedic intervention have demonstrated efficacy. Systemic treatment with anti-osteoporotic drugs is effective, but the potential harm to the fetus imposes caution in their use.

Clinical Recommendations for the Use of Islet Cell Autoantibodies to Distinguish Autoimmune and Non-Autoimmune Gestational Diabetes

“…The maternal kidneys, and possibly the placenta, decidua, and fetal kidneys, try to meet this increased vitamin D requirement by providing the necessary 1-α hydroxylase activity; this enzyme hydroxylates vitamin D metabolite 25-hydroxycolecalciferol into biologically active 1α,25-dihydroxycolecalciferol [1,25(OH) 2 D 3 ]. The result of this process is a several-fold increase in serum vitamin D level in healthy pregnancy compared with the prepregnancy level [65]. However, the prevalence of vitamin D deficiency is increased among pregnant women, despite sufficient exposure to sunlight [66].…”

Training Characteristics During Pregnancy and Postpartum in the World’s Most Successful Cross Country Skier

“…In this connection, a decrease in the BMD after delivery and further lowering to PP3 was observed. The reason for this might be that the fetal skeleton requires a substantial transfer of calcium during Tri-3 and, in addition, loss of calcium in breast milk (Sanz-Salvador et al, 2015). Currently, the mechanisms behind calcium transfer and bone turnover during pregnancy and lactating are only partly understood and there is a lack of knowledge considering the effect of exercise on these factors.…”

“…A marathon runner reported a training volume as high as 50 km during the initial week postpartum, which was progressively increased to 98 km during week 14 without any major problems (Potteiger et al, 1993). However, drainage of calcium from maternal skeleton during late pregnancy and calcium loss due to breast milk production could potentially lead to increased risk of fragility fractures during the postpartum period (Woodrow et al, 2006; Kovacs, 2011; Sanz-Salvador et al, 2015). …”

Theobromine Upregulates Osteogenesis by Human Mesenchymal Stem Cells In Vitro and Accelerates Bone Development in Rats

“…The public health significance of this study is highlighted by reports that skeletal growth and development can be significantly inhibited in humans in utero through exposure to alcohol [20, 21], nicotine [20, 22], maternal disease [20] and malnutrition [23]. Even when exposure to toxins and nutritional deficits are resolved, reversal of the effects are challenging because administration of anabolic drugs to pregnant mothers and infants can be associated with serious safety concerns [24–26]. With its excellent safety profile [2, 27, 28], GRAS status, natural origin and abundancy, excellent oral bioavailability and long plasma half-life [29, 30], THB may serve as a safe and effective natural osteoanabolic supplement.…”