Serum Osteoprotegerin as a Determinant of Bone Metabolism in a Longitudinal Study of Human Pregnancy and Lactation

• Published in: The journal of clinical endocrinology and metabolism 2003-11, Vol.88 (11), p.5361-5365
• Main Authors: Naylor, K. E., Rogers, A., Fraser, R. B., Hall, V., Eastell, R., Blumsohn, A.
• Format: Article
• Language: English
• Subjects: Adult; Biological and medical sciences; Bone and Bones - metabolism; Bone Density; Carrier Proteins - metabolism; Diseases of mother, fetus and pregnancy; Estrogens - blood; Female; Glycoproteins - blood; Gynecology. Andrology. Obstetrics; Humans; Infant, Newborn; Lactation - physiology; Longitudinal Studies; Medical sciences; Membrane Glycoproteins - metabolism; Osteoprotegerin; Postpartum Period - metabolism; Pregnancy - metabolism; Pregnancy. Fetus. Placenta; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B; Receptors, Cytoplasmic and Nuclear - blood; Receptors, Tumor Necrosis Factor
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2003-030486

Osteoprotegerin (OPG) is a soluble decoy receptor that inhibits bone resorption by binding to receptor activator of nuclear factor κB ligand. Murine studies suggest that OPG is elevated in pregnancy, but its role in human pregnancy is unknown. We evaluated the relationship among OPG, bone turnover, and bone density in a longitudinal study of planned human pregnancy and lactation (n = 17; age, 20–36 yr). Samples were collected before conception; at 16, 26, and 36 wk gestation; and at 2 and 12 wk postpartum. Indexes of bone resorption included serum β C-terminal and urinary N-terminal (uNTX) telopeptides of type I collagen. OPG increased by 110 ± 16% (mean ± sem) at 36 wk (P < 0.001), followed by a rapid postpartum decline in both lactating and nonlactating women. Bone resorption was elevated at 36 wk (serum β C-terminal telopeptides by 76 ± 17%; urinary N-terminal telopeptides by 219 ± 41%; P < 0.001). The tissue source of OPG in pregnancy is unknown. Human breast milk contains large amounts of OPG (162 ± 58 ng/ml in milk vs. 0.42 ± 0.03 ng/ml in nonpregnant serum). However, the rapid postpartum decline in serum OPG and the low serum OPG in neonates suggest a placental source. There was no correlation between change in OPG and bone turnover or bone mineral density (P > 0.05), and the physiological importance of elevated OPG in human pregnancy remains uncertain.