Parathyroid Hormone-Related Protein-Induced Hypercalcemia of Pregnancy Successfully Reversed by a Dopamine Agonist

Context: Parathyroid hormone-related protein (PTH-rP)-induced hypercalcemia or pseudophyperparathyroidism during pregnancy is a condition that can result in serious fetal and maternal complications. Among others, breast tissue might be the cause of this PTH-rP production, in which case medical treatment is possible, as we describe in this case. Setting: A 32-year-old woman presented in the 15th week of pregnancy with massive enlargement of breasts and abdominal pain due to severe hypercalcemia, hypercalciuria, and suppressed PTH. Hematological and solid malignancy were excluded. PTH-rP was found to be fourfold to eightfold increased, which is pathological even for pregnancy term. PTH-rP is produced in mammarian tissue as well as in placental tissue, in reaction to prolactin receptor activation. Prolactin hypersensitivity of breast tissue can cause excessive PTH-rP production during pregnancy. Intervention: Dopamine agonists were applied to decrease prolactin. Results: Calcium levels normalized, and PTH-rP levels became undetectable with bromocriptin treatment. A full-term healthy baby was born without disorders of calcium homeostasis, neither directly after birth nor 2 years after follow-up. After delivery, dopamine agonists could be tapered without recurrence of hypercalcemia. Conclusion: Pseudohyperparathyroidism of pregnancy was caused by increased sensitivity of mammarian tissue for prolactin, which could be treated medically, preventing emergency mastectomy.