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A metabolic complication of pregnancy

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Q1: What are the findings on the ultrasound in figs 1 and 2?

The ultrasound image of the kidneys (fig 1; p 55) shows marked bilateral renal medullary calcification (nephrocalcinosis). The ultrasound image of the parathyroids (p 55) shows a parathyroid adenoma with the Doppler signal produced by the blood flow to the adenoma.

Box 1: Causes of nephrocalcinosis

  • Medullary sponge kidney

  • Primary hyperparathyroidism

  • Hypercalciuria

  • Hypervitaminosis D

  • Sarcoidosis

  • Fabry's disease

  • Wilson's disease

Q2: How should this patient be managed?

This patient should have a parathyroidectomy during the second trimester.

OUTCOME IN THIS CASE

The patient's blood pressure remained well controlled on methyldopa and at 20 weeks' gestation she had the parathyroid adenoma removed under general anaesthesia. The diagnosis was confirmed on histology. Her serum calcium fell to 2.34 mmol/l postoperatively and has since remained normal. She gave birth to a normal baby girl at term. Following surgery she remained normotensive, even after the methyldopa was discontinued.

Discussion

Hyperparathyroidism during pregnancy is uncommon, with just over 100 cases reported since the first description by Hunter in 1931. The incidence is not known; however, in all women of child bearing age the annual incidence of new cases is said to be about 8/100 000 population.1 This condition results in a 20–30% incidence of fetal or neonatal death and an incidence of complications during pregnancy exceeding 50% if untreated.2Physiological adjustment during pregnancy maintains calcium homeostasis despite increased requirements (approximately 30 g) for fetal skeletal development. Intact parathormone levels remain largely unchanged or diminish during pregnancy.3 Total serum calcium decreases, reflecting a fall in serum albumin. A consistent increase in maternal vitamin D3 levels with advancing gestation ensures that the fetal requirements for calcium are met through increased intestinal absorption of calcium.4 The clinical presentation of hyperparathyroidism during pregnancy is similar to that found in the general population, and many patients are asymptomatic. Untreated primary hyperparathyroidism increases the risk of fetal loss, neonatal morbidity (in particular tetany), and mortality. None of the medical treatments presently available is safe in pregnancy. There have been anecdotal reports of the successful use of oral phosphate.5 Current recommendations for the treatment of hyperparathyroidism during pregnancy advocate surgery during the second trimester.6 Our patient underwent surgery without any adverse effect at 20 weeks. It is prudent to avoid surgery during the first trimester until the completion of organogenesis, and in the third trimester, when there is an increased risk of spontaneous labour. There is an association of hypertension with hyperparathyroidism, the cause of which is unknown. This patient's hypertension was cured following surgery. Nephrocalcinosis is known to result from primary hyperparathyroidism and it remains to be seen if it will resolve in this patient.

In conclusion, when hyperparathyroidism is suspected in pregnancy, efforts should be made to make an early definitive diagnosis so that surgery can be planned for the second trimester. In patients with parathyroid adenoma, surgery at this stage is usually associated with successful maternal and fetal outcomes.

Learning points Hyperparathyroidism in pregnancy

  • Clinical presentation during pregnancy is similar to that found in the general population and it is sometimes diagnosed retrospectively following the birth of the baby.

  • If untreated, it results in a substantial increase in morbidity and mortality in the newborn infant.

  • Surgery during second trimester is the treatment of choice.

References

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