Differential Diagnosis for Elevated PTH, Normal Corrected Calcium, High 24-Hour Urine Calcium, Recurrent Renal Stones, and Primary Hypothyroidism

• Single Most Likely Diagnosis
  • Primary Hyperparathyroidism: This condition is characterized by elevated parathyroid hormone (PTH) levels, which can lead to hypercalcemia, although in this case, the corrected calcium is normal. The high 24-hour urine calcium and recurrent renal stones are consistent with the effects of excess PTH on calcium metabolism. Primary hypothyroidism can sometimes be associated with or exacerbate the symptoms of primary hyperparathyroidism.
• Other Likely Diagnoses
  • Familial Hypocalciuric Hypercalcemia (FHH): Although calcium levels are normal in this case, FHH can sometimes present with normal or slightly elevated calcium levels and is characterized by elevated PTH and low urinary calcium excretion, which does not perfectly match this scenario but could be considered if the high urine calcium is intermittent.
  • Lithium-Induced Hyperparathyroidism: Lithium therapy can cause elevated PTH levels and may lead to hypercalcemia and increased urine calcium, similar to primary hyperparathyroidism. The presence of primary hypothyroidism might be coincidental or related to lithium treatment, which can also affect thyroid function.
• Do Not Miss Diagnoses
  • Multiple Endocrine Neoplasia (MEN) Syndromes: These are hereditary conditions that can involve multiple endocrine glands, including the parathyroids, thyroid, and others. MEN syndromes could explain the combination of primary hypothyroidism and elevated PTH, especially if other endocrine abnormalities are present.
  • Parathyroid Carcinoma: A rare cause of primary hyperparathyroidism, which could present with elevated PTH, normal or elevated calcium levels, and high urine calcium. It's crucial to consider this diagnosis due to its potential for severe outcomes if left untreated.
• Rare Diagnoses
  • Neonatal Severe Primary Hyperparathyroidism: Extremely rare and typically presents in infancy, but could be considered in very rare cases where familial conditions lead to early onset of hyperparathyroidism symptoms.
  • Teriparatide or PTH Analog Therapy: Although not a disease, exogenous administration of PTH or its analogs for conditions like osteoporosis could lead to elevated PTH levels and increased urine calcium, and should be considered in the differential if the patient has a history of such treatment.