The most common causes of hypoparathyroidism are inadequate secretion of parathyroid hormone after interruption of the blood supply, or surgical removal of parathyroid gland tissue during thyroidectomy, parathyroidectomy, or radical neck dissection. Atrophy of the parathyroid glands of unknown etiology is a less common cause. Symptoms are due to deficiency of parathormone, which results in an elevation of blood phosphate (hyperphosphatemia) and a decrease in blood calcium levels (hypocalcemia).

• Tetany is the chief symptom caused by hypocalcemia.
• Latent tetany is characterized by numbness, tingling, and cramps in the extremities; stiffness in the hands and feet.
• Overt tetany is marked by bronchospasm, laryngeal spasm, carpopedal spasm, dysphagia, photophobia, cardiac dysrhythmias, and seizures.
• Other symptoms include anxiety, irritability, depression, and delirium. Electrocardiogram (ECG) changes and hypotension may also occur.

• Latent tetany is suggested by a positive Trousseau sign (in which carpopedal spasm is induced by occluding the blood flow to the arm for 3 minutes with a blood pressure cuff) or a positive Chvostek sign (in which sharp tapping over the facial nerve just in front of the parotid gland and anterior to the ear causes spasm or twitching of the mouth, nose, and eye).
• Diagnosis is difficult because of vague symptoms such as aches and pains; laboratory studies show increased serum phosphate, with serum calcium of 5 to 6 mg/dL (1.2 to 1.5 mmol/L) or lower; x-rays of bone show increased density and calcification of the subcutaneous or paraspinal basal ganglia of the brain.

• Raise serum calcium level to 9 to 10 mg/dL (2.2 to 2.5 mmol/L).
• When hypocalcemia and tetany occur after thyroidectomy, IV calcium gluconate is given immediately. Sedative agents (pentobarbital) may be given. Parenteral parathormone may be given, but watch for an allergic reaction and changes in serum calcium levels.
• Neuromuscular irritability is reduced by providing an environment that is free of noise, drafts, bright lights, or sudden movement.
• Tracheostomy, or mechanical ventilation and bronchodilating medications, may become necessary if the patient develops respiratory distress.
• Chronic hypoparathyroidism is treated with a diet high in calcium and low in phosphorus. Patient should avoid milk, milk products, egg yolk, and spinach.
• Provide combinations of calcitriol, calcium, magnesium, and vitamin D₂ (ergocalciferol) or vitamin D₃ (cholecalciferol), the latter being preferred. Administer a thiazide diuretic (e.g., hydrochlorothiazide) to help decrease urinary calcium excretion. Oral calcium tablets and vitamin D preparations, as well as aluminum hydroxide gel or aluminum carbonate, may be given after meals.

• Detect early signs of hypocalcemia and anticipate signs of tetany, seizures, and respiratory difficulties.
• Keep calcium gluconate at the bedside; if patient has a cardiac disorder, is subject to dysrhythmias, or is receiving digitalis, the calcium gluconate is given slowly and cautiously.
• Provide continuous cardiac monitoring and careful assessment; calcium and digitalis increase systolic contraction and also potentiate each other; this can produce potentially fatal dysrhythmias.
• Educate patient about medications and diet therapy, the reason for high calcium and low phosphate intake, and the symptoms of hypocalcemia and hypercalcemia.
• Direct patient to contact physician if symptoms occur.

For more information, see Chapter 52 in Hinkle, J. L., & Cheever, K. H. (2018). Brunner and Suddarth's textbook of medical-surgical nursing (14th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.