Hypoparathyroidism for PA
Hypoparathyroidism for the Physician Assistant Licensing Exam
- Pathophysiology
- Hypoparathyroidism is characterized by insufficient secretion or action of parathyroid hormone (PTH), leading to hypocalcemia and hyperphosphatemia.
- PTH typically increases calcium by promoting bone resorption, enhancing renal calcium reabsorption, and activating vitamin D to improve intestinal absorption of calcium.
- In hypoparathyroidism, these functions are impaired, leading to decreased calcium levels and elevated phosphate levels.
- Etiology
- Post-Surgical Hypoparathyroidism: The most common cause, often following thyroidectomy, parathyroidectomy, or neck surgery.
- Autoimmune Destruction: Can occur as part of autoimmune polyglandular syndrome.
- Congenital Disorders: Such as DiGeorge syndrome, characterized by congenital absence or malformation of the parathyroid glands.
- Radiation Therapy: Damage to the parathyroid glands following radiation to the neck or head.
- Magnesium Imbalance: Severe hypomagnesemia can impair PTH secretion.
- Clinical Features
- Neuromuscular Symptoms:
- Tetany: Muscle cramps and spasms, especially in the hands and face.
- Chvostek’s Sign: Twitching of facial muscles when the facial nerve is tapped.
- Trousseau’s Sign: Carpal spasm induced by inflating a blood pressure cuff.
- Paresthesia: Tingling or numbness around the mouth and extremities.
- Cardiovascular Symptoms:
- Prolonged QT Interval: Hypocalcemia can prolong the QT interval on ECG, increasing the risk of arrhythmias.
- Other Symptoms: Irritability, anxiety, depression, and cognitive disturbances in chronic cases.
- Diagnosis
- Laboratory Findings: Low serum calcium, high serum phosphate, and low PTH levels.
- Magnesium Levels: Hypomagnesemia should be assessed and corrected.
- ECG: May show a prolonged QT interval due to hypocalcemia.
- Management
- Acute Hypocalcemia: IV calcium gluconate for patients with severe hypocalcemia, such as those experiencing tetany or arrhythmias.
- Chronic Hypocalcemia:
- Oral Calcium: Long-term calcium supplementation.
- Vitamin D (Calcitriol): Necessary to promote calcium absorption in patients with hypoparathyroidism.
- Thiazide Diuretics: May reduce calcium excretion and prevent kidney stones.
- Magnesium: Correction of hypomagnesemia is essential for improving PTH function.
Key Points
- Hypoparathyroidism is characterized by low PTH levels, leading to hypocalcemia and hyperphosphatemia. Post-surgical causes are most common.
- Symptoms include tetany, paresthesia, prolonged QT interval, and neuropsychiatric disturbances. Severe hypocalcemia can cause life-threatening complications.
- Management includes acute IV calcium for symptomatic patients, along with long-term oral calcium and vitamin D supplementation.