Endocrine Abstracts

A lactating 31-year-old woman who developed L5 vertebral compression fracture 2 months after the delivery of her first child is presented. Serum concentrations of Ca was 10.24 mg/dl (8.6–10.2 mg/dl), phosphorus was 4.1 mg/dl (2.7–4.5 mg/dl), albumin was 4.6 mg/dl, ALP was 210 U/l (35–105 U/l), PTH was 13.8 pg/ml (15–65). There was axial osteoporosis, as assessed by dual-energy X-ray absorptiometry. Z score; L1 (−3), L2 (−3.8), L3 (−3.8), L4 (−3.6). CCr 127 ml/min, 24 h Ca excretion was 153.4 mg. 25-hydroxyvitamin D was 10.9 ng/ml. Causes for secondary osteoporosis were excluded. She was diagnosed as postpartum osteoporosis associated with hypercalcemia and probable parathyroid hormon-related protein (PTHrP) hypersecretion. Studies have established that the exogenous production of vitamin D requirements fall during breast-feeding through a PTHrP and prolactin mediated mechanisms. PTHrP is known to be physiological present in some tissues, especially in brest milk. Production of PTHrP from the mammary gland in response to elevated prolactin and lower estradiol levels leads to calcium and phosphate mobilization from bone. Its role in control of total milk calcium content is postulated, and PTHrP may also regulate mammary blood flow through vasodilatory mechanisms. Our case highlights the importance of the possible aetiological role for parathyroid hormone-related peptide in derangements in calcium metabolism with postpartum osteoporosis during lactation.