Differential Diagnosis for Elevated PTH with Normal GFR, Calcium, and Vitamin D
Single Most Likely Diagnosis
- Primary Hyperparathyroidism: This condition is characterized by the excessive production of parathyroid hormone (PTH) due to one or more parathyroid glands being overactive. It is the most common cause of hyperparathyroidism and can lead to elevated PTH levels even when calcium and vitamin D levels are within the normal range, especially in its early stages or mild forms.
Other Likely Diagnoses
- Familial Hypocalciuric Hypercalcemia (FHH): Although calcium levels are normal in this scenario, FHH can sometimes present with normal calcium levels, and it's characterized by an inherited trait leading to altered calcium sensing by the parathyroid glands, resulting in elevated PTH.
- Lithium-Induced Hyperparathyroidism: Lithium therapy can lead to increased PTH secretion, potentially causing elevated PTH levels even with normal calcium and vitamin D levels.
- Vitamin D Receptor Mutations: Certain mutations affecting the vitamin D receptor can lead to resistance to vitamin D, potentially causing secondary hyperparathyroidism with elevated PTH levels despite normal vitamin D levels.
Do Not Miss Diagnoses
- Parathyroid Cancer: Although rare, parathyroid cancer can cause elevated PTH levels and should not be missed due to its significant implications for treatment and prognosis.
- Multiple Endocrine Neoplasia (MEN) Syndromes: These syndromes can include primary hyperparathyroidism as part of their clinical presentation and are critical to diagnose due to their potential for other serious endocrine disorders.
- Hyperparathyroidism-Jaw Tumor Syndrome: A rare genetic disorder that can cause hyperparathyroidism and should be considered to avoid missing a potentially treatable condition.
Rare Diagnoses
- Neonatal Severe Primary Hyperparathyroidism: An extremely rare condition usually diagnosed in infancy, characterized by very high levels of PTH, but could potentially present with less severe biochemical abnormalities in some cases.
- Parathyroid Hyperplasia: Can be a cause of elevated PTH, though less common than adenoma in primary hyperparathyroidism, and might be considered in the differential diagnosis, especially if other causes are ruled out.