Hyperparathyroidism, hypercalcaemia

1. Big picture

This topic is about too much calcium in the blood and the most important endocrine cause: hyperparathyroidism.

For the exam, always start with one question:

Is hypercalcaemia PTH-dependent or PTH-independent?

Because the first diagnostic fork is:

High or inappropriately normal parathyroid hormone (PTH) → primary/tertiary hyperparathyroidism, familial hypocalciuric hypercalcaemia, lithium/thiazides. Suppressed PTH → malignancy, vitamin D excess, granulomatous disease, thyrotoxicosis, adrenal insufficiency, immobilization, drugs.

Primary hyperparathyroidism is usually an outpatient, chronic, often mild disease. Malignancy-related hypercalcaemia is usually more acute, more severe, and more dangerous.

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