Severe postpartum osteoporosis with increased PTHrP during lactation in a patient after total thyroidectomy and parathyroidectomy

We present a 27-year-old woman with hypoparathyroidism following total thyroidectomy for papillary carcinoma, who presented postpartum during lactation with several vertebral osteoporotic fractures, increase in bone turnover markers, and measurable parathyroid hormone-related protein (PTHrP) levels. Cessations of lactation led to gradual decrease in bone turnover markers and PTHrP and improvement in bone mineral density. Pregnancy- and postpartum-associated osteoporosis is an uncommon condition characterized by the occurrence of fractures during late pregnancy or the puerperium. The patient presented postpartum with severe back pain and multiple vertebral fractures. Metabolic evaluation performed at presentation revealed hypercalcemia, hypercalciuria, increased alkaline phosphatase, vitamin D insufficiency, normal serum protein immunoelectrophoresis, and a detectable level of PTHrP. Serum levels of bone turnover markers were markedly increased. Bone mineral density at the lumbar spine was severely reduced. After cessation of lactation, the PTHrP level became undetectable. Bone turnover markers gradually decreased to normal and bone mineral density improved. Several factors contributed to the reduced bone mass in this patient, including amenorrhea treated with oral contraceptives, suppressive levothyroxine treatment, and lactation of twins with increased PTHrP. Patients with severely reduced bone mass need surveillance during pregnancy and lactation and should possibly consider avoiding breastfeeding. Patients with hypoparathyroidism should temporarily reduce their alphacalcidiol dose while lactating.