HYPOPARATHYROIDISM
Hypoparathyroidism results from a deficiency of parathyroid hormone and is characterized by hypocalcaemia and neuromuscular hyperexcitability.
Causes
1. Infection, hereditary
2. Interruption of blood supply or surgical removal of parathyroid gland tissue during thyroidectomy, parathyroidectomy or radical neck dissection.
3. Decrease in gland function; may be autoimmune or familial in origin.
4. Malignancy or metastasis from a cancer to the parathyroid glands.
Pathophysiology
Inadequate PTH secretion
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Decreased absorption of Ca in the GIT, decreased resorption of Calcium from the renal tubules and decreased resorption of Ca from bone.
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Blood calcium falls to a low level
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Muscular hyperirritability, uncontrolled spasms and hypocalcaemic tetany
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Decrease serum calcium and lack of PTH
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Serum phosphate level rise
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Decrease excretion of phosphate by the kidneys
Clinical Manifestations
[Hypocalcaemia, irritability of the neuromuscular system]
1. Tetany general muscular hypertonia, with tremor and spasmodic or uncoordinated contractions occurring with or without efforts to make voluntary movements.
a. Chvostek's sign
b. Trousseau's sign-
Later tetany numbness, tingling and cramps in the extremities with complaints of stiffness in the hands and feet.
Overt tetany bronchospasm, laryngeal spasm, carpopedal spasm (flexion of the elbows and wrists and extension of the carpophalangeal joints), dysphagia, photophobia, cardiac arrhythmias and convulsions.
2 Anxiety, irritability, depression and delirium.
Diagnostic Evaluation
1. Latent tetany Positive Trousseau's sign (Carpopedal spasm is inducing by occluding blood flow to the arm for 3 mins using a BP cuff)
2. Positive Chvostek's sign.
3. Phosphorus level in blood is elevated.
4. Decrease in serum calcium level to a low level (7.5 mg/100 ml or less).
5. X-ray studies of bone-show increased density
6. Calcification is noticed on x-ray films of subcutaneous or paraspinal basal ganglia of the brain.
Medical Management
1. IV calcium administration.
(i) Calcium chloride [-500 mg 1 gm (5-10 ml) as indicated by serum calcium; administer at rate of < 1 ml/min of 10% solution].
(ii) Calcium gluconate [500 mg 2g (1020 ml) at the rate of 20.5ml/min of a 10% solution].
(iii) Calcium gluceptate- [1-2 g (5-10 ml) at a rate of < 1 ml/min].
All calcium preparations are administered slowly, It is highly irritating, stings and causes thrombosis. Patient experiences unpleasant burning flush of skin and tongue [A slow drip of IV saline containing calcium gluconate is given until control of tetany is ensured; then intramuscular or oral administration of calcium is prescribed]
Later, Vitamin D is added to calcium intake increases the absorption of calcium and also induces a high level of calcium in the bloodstream
2. Parenteral parathormone can be administered to treat acute hypoparathyroidism with tetany
3. The patient with hypocalcaemia and tetany requires an environment that is free of noise, sudden drafts, bright lights or sudden movement because of neuromuscular irritability.
4. Treat kidney stones.
5 Tracheostomy or mechanical ventilation may become necessary, along with broncho dilating medications, if the patient develops respiratory distress.
Complications
1. Related to hypocalcaemia with calcium therapy] seizures, tetany and mental disorders [can be reversed
2. Acute hypocalcaemia cardiovascular failure. laryngeal spasm, acute airway obstruction and
3. Long-term complications subcapsular cataracts, calcification of the basal ganglia and papilledema, (caused by precipitation of calcium out of serum and deposition in tissue); shortening of the fingers and toes, and bowing of the long bones (caused by inadequate PTH and additional genetic abnormalities).
Nursing Interventions
1 Assess neuromuscular status, check for Trousseau's and Chvostek's signs and notify physician.
2. Assess respiratory status frequently in acute hypocalcaemia and postoperatively.
3. Promote high- calcium diet if prescribed dairy products, green leafy vegetables and low in phosphorus
4. Use caution in administering other drugs to the patient with hypocalcaemia
5. Explain to the patient; and family the function of PTH and the roles of vitamin D and of calcium in maintaining good health.
6. Explain the need for periodic medical follow-up for life
7. Aluminum hydroxide gel or aluminum carbonate (Gelusil, Amphojel) is also given after meals to bind phosphate and promote its excretion through the GI tract.
