Understanding Hyperparathyroidism: Causes and Symptoms

Hyperparathyroidism is a condition characterized by excessive production of parathyroid hormone (PTH), leading to elevated levels of calcium in the blood (hypercalcemia). The most common cause of this condition, accounting for approximately 80% of cases, is a benign tumor known as a parathyroid adenoma. The remaining cases typically arise from hyperplasia, where all parathyroid glands enlarge. While parathyroid cancer is rare, it is essential to consider multiple endocrine neoplasia (MEN) type 1 in younger patients presenting with primary hyperparathyroidism.

The condition can be classified into primary, secondary, and tertiary forms. Primary hyperparathyroidism usually stems from the overactivity of the parathyroid glands due to adenomas or hyperplasia. Secondary and tertiary hyperparathyroidism often develop in individuals with renal failure, where the kidneys fail to properly process vitamin D. This failure triggers an increase in PTH levels as the body attempts to maintain normal calcium levels, potentially leading to osteodystrophy—a weakening of bone structure.

Hypercalcemia can be caused by other factors beyond hyperparathyroidism. Malignancies are a significant contributor, as several types of cancer, including those of the lung, breast, prostate, kidney, and thyroid, commonly metastasize to bone, leading to calcium elevation. Other less common causes include familial benign hypercalcemia, thyrotoxicosis, hypoadrenalism, and acromegaly.

When investigating suspected primary hyperparathyroidism, specific laboratory tests are crucial. Patients typically present with serum calcium levels that are elevated, while PTH levels may be either inappropriately normal or elevated. It's important to note that vitamin D deficiency, common in the UK, can also raise PTH levels, making it vital to confirm that calcium levels are genuinely elevated. A 24-hour urinary calcium test usually reveals increased calcium excretion in primary hyperparathyroidism.

Symptoms of hyperparathyroidism can be vague and often go unnoticed in mild cases, which are frequently identified through routine blood tests. Classic symptoms associated with more severe hypercalcemia include the phrase "bones, stones, abdominal groans, and psychic moans," reflecting the diverse effects of high calcium levels on bones, kidneys, gastrointestinal health, and mental well-being. Understanding these symptoms and the underlying causes of hyperparathyroidism is essential for proper diagnosis and management.