Post-pregnancy osteoporosis associated with hypercalcaemia.

A lactating 31-year-old woman who developed four vertebral fractures 1-2 months after the delivery of her first child is described. She was hypercalcaemic (serum calcium up to 2.99 mmol/l), and urinary excretion of both calcium and hydroxyproline (an index of bone resorption) were markedly elevated. Serum levels of parathyroid hormone and 1,25-dihydroxyvitamin D were suppressed, but parathyroid hormone-related peptide was above normal. There was severe axial osteopenia, as assessed by dual-energy X-ray absorptiometry. The biochemical abnormalities were reversed within 2 weeks of weaning, with the exception of the parathyroid hormone-related peptide concentration, which declined more gradually. This appears to be the first description of the abnormalities in calcium metabolism and bone density from early in the course of post-pregnancy osteoporosis and it indicates that this condition is associated with high levels of osteolysis which return to normal after weaning. This rapid reversal of the metabolic abnormalities accounts for the inconclusive nature of previous descriptions of post-pregnancy osteoporosis, in which investigations were more delayed. It also emphasizes the importance of weaning in the management of women presenting with this condition. A possible aetiological role for parathyroid hormone-related peptide is discussed.