Differential Diagnosis for Hyperparathyroidism
Single Most Likely Diagnosis
- Primary Hyperparathyroidism: This is the most common cause of hyperparathyroidism, typically due to a single parathyroid adenoma (about 80-85% of cases), less commonly due to parathyroid hyperplasia (about 15-20% of cases), and rarely due to parathyroid carcinoma. The condition leads to excessive production of parathyroid hormone (PTH), causing hypercalcemia.
Other Likely Diagnoses
- Familial Hypocalciuric Hypercalcemia (FHH): A genetic disorder that affects the calcium-sensing receptor, leading to mild hypercalcemia and inappropriately normal or elevated PTH levels. It's a benign condition but can be confused with primary hyperparathyroidism.
- Lithium-Induced Hyperparathyroidism: Long-term lithium therapy can lead to hyperparathyroidism by increasing PTH secretion. This condition resolves after discontinuation of lithium but may require surgical intervention if severe.
- Vitamin D Deficiency: Although it typically causes secondary hyperparathyroidism, severe deficiency can lead to increased PTH levels, which may mimic primary hyperparathyroidism.
Do Not Miss Diagnoses
- Parathyroid Carcinoma: A rare cause of primary hyperparathyroidism, but it's crucial to identify due to its potential for malignancy and the need for prompt surgical intervention.
- Multiple Endocrine Neoplasia (MEN) Syndromes: Specifically, MEN1 and MEN2A, which can include primary hyperparathyroidism as part of their syndrome. Identifying these conditions is critical due to the presence of other potentially malignant endocrine tumors.
- Hypercalcemia of Malignancy: Although not a direct cause of hyperparathyroidism, malignancies (like lung, breast, and kidney cancers) can produce PTH-related protein (PTHrP), leading to hypercalcemia that mimics hyperparathyroidism.
Rare Diagnoses
- Teriparatide (PTH analogue) Therapy: Used for osteoporosis treatment, it can cause elevated PTH levels, mimicking hyperparathyroidism.
- Ectopic Production of PTH: Extremely rare, where PTH or a PTH-like substance is produced by non-parathyroid tissues, often in the context of a tumor.
- Iron Overload: Can lead to an increase in PTH levels, though this is more commonly associated with secondary hyperparathyroidism in the context of chronic kidney disease.