Hypoparathyroid Disease PDF

Hypoparathyroid Definition: ○ Hypoparathyroid disease is an endocrine disorder with multiple causes that is characterized by subnormal secretions of parathyroid hormone (PTH) into the blood ○ As a result, patients suffer symptoms due to low levels of serum...

Hypoparathyroid Definition: ○ Hypoparathyroid disease is an endocrine disorder with multiple causes that is characterized by subnormal secretions of parathyroid hormone (PTH) into the blood ○ As a result, patients suffer symptoms due to low levels of serum calcium ○ The condition can be congenital or acquired either permanent or temporary Prevalence: ○ The overall incidence of hypoparathyroid disease today in the United States has been estimated at approximately 4 cases in 100,000 persons, a prevalence of approximately 12,000 americans ○ There are numerous causes of hypoparathyroid disease, but the condition most commonly results from injury to or removal of the parathyroid glands at the time of parathyroid or thyroid surgery ○ Postoperatuvely induced hypoparathyroid disease occurs in approximately 1% of all individuals who undergo thyroid surgery, with the frequency increasing to 10% after repeated neck explorations Significance ○ The significance of hypoparathyroidism lies primarily in its clinical symptoms and complications ○ The most serious acute complications are tetany (i.e., severe and painful muscle cramps of the entire body), laryngeal and bronchial spasms that can cause respiratory tract obstruction and asphyxiation, and tonic-clonic seizures. ○ Without calcium therapy, patients can die Causes and risk factors ○ There are many potential causes of hypoparathyroid disease, and they can be classified as iatrogenic (i.e., treatment-induced), autoimmune, congenital, metal overload-induced, infiltration related, and hypomagnesemia-induced ○ A lengthy list of specific conditions that cause hypoparathyroidism has been published by Goltzman and Cole (1996) ○ The most common cause of iatrogenic hypoparathyroidism and the most common cause of hypoparathyroid disease overall is surgical excision of parathyroid gland tissue in the treatment of thyroid, parathyroid, laryngeal or other diseases of the neck ○ Attempts as restoring normal PTH levels by transplantation of a fraction of one of the parathyroid glands cryopreserved during surgery are sometimes effective, but most patients (¾) become hypoparathyroid ○ Autoimmune polyglandular syndrome type 1 is one cause of autoimmune disease within parathyroid tissue  ○ The average age for development of symptoms related to autoimmune induced hypoparathyroidism is 7 years with a range of 6 months to 20 years. ○ In autoimmune induced hypoparathyroid disease, components of the immune system attack and destroy parathyroid tissue ○ Congenital causes are numerous and include X-linked, autosomal recessive, and autosomal dominant hypoparathyroidism (in which mutations of the CaSR and GATA3 genes have been identified); diabetic, alcohol, and retinoid embryopathies; and DiGeorge syndrome, in which children are born without parathyroid glands. ○ Causes related to metal overload include hemochromatosis and thalassemia, both of which are associated with iron overload; ○ Wilson disease, which is characterized by copper overload; ○ End-stage renal disease, in which aluminum deposits destroy parathyroid glands in patients undergoing hemodialysis. ○ Infiltration-related hypoparathyroidism is the result of systemic disease that injures the parathyroid glands, for example, cancer that metastasizes to the parathyroids or infection (like syphilis) that involves the parathyroid glands. ○ Hypoparathyroid disease may also occur as a result of magnesium deficiency (e.g., the result of malabsorption in the gastrointestinal tract or poor nutrition from alcohol abuse). ○ Low serum levels of magnesium inhibit the secretion of PTH. ○ Obviously, this type of hypoparathyroidism is reversible with magnesium salt therapy. Pathophysiology ○ Parathyroid hormone has four major physiologic effects to elevate serum calcium levels when they are low: 1. PTH activates osteoclasts, which resorb or break down bone, resulting in the release of ionized calcium into the blood. 2. PTH inhibits the reabsorption of phosphate by renal proximal tubules, resulting in an increase in phosphate excretion in the urine and an increase in serum calcium concentration. 3. PTH increases calcium reabsorption in the renal distal tubules. 4. PTH stimulates the activity of renal 1-α-hydroxylase, a critical enzyme in the synthesis of 1,25-dihydroxyvitamin D, which promotes better dietary calcium absorption in the gastrointestinal tract. Diagnosis: ○ Patients with hypoparathyroidism often complain of the following symptoms: paresthesias (i.e., tingling, burning, or “pins and needles” sensations) around the mouth and in the fingertips and toes  twitching and painful muscle spasms of the lower back, abdomen, hands, and feet lethargy anxiety hyperirritability mood swings thin and brittle nails dry and scaly skin hair loss Clinical signs of hypocalemia from hypoparathyroid disease include: ○ positive Chvostek sign in which unilateral facial twitching, especially around the mouth, is induced by gently tapping the ipsilateral facial nerve just anterior to the ear ○ positive Trousseau sign in which carpal spasm (i.e., downward flexion of the wrist) is induced by inflating a blood pressure cuff around the arm to a pressure 20 mm Hg above the systolic blood pressure for 3–5 minutes ○ prolongation of the QT interval on the electrocardiogram ○ basal ganglia calcifications observed with computed tomography (CT) scans of the skull ○ cataract formation observed with slit-lamp examination of the eyes Serious complications and prognosis ○ The most serious acute complications of hypoparathyroid disease were described above and include tetany, convulsions, and respiratory tract obstruction leading to asphyxiation ○ Chronic hypoparathyroidism can cause cataracts and Parkinson-like symptoms in adults and defective teeth and bone development and mental retardation in children. ○ The outlook for recovery is good if diagnosis and treatment are prompt. Patients can expect to live a near-normal life. ○ Dental abnormalities, cataracts, and brain calcifications are irreversible and do not remit with treatment. Appropriate therapy ○ The primary goal of therapy is to maintain the serum calcium concentration in a slightly low but mild asymptomatic range (8.0–8.6 mg/dL) to minimize hypercalciuria and prevent hypercalcemia from overdosing. ○ Monitoring serum calcium levels at least every 3 months is mandatory. ○ Urine calcium levels should be maintained ○ below 30 mg/dL, if possible. ○ A diet rich in calcium (e.g., dairy products) is recommended. ○ Activity in patients with symptomatic ○ hypocalcemia may cause tetany. ○ Otherwise, no restriction in activity is necessary. ○ Magnesium supplementation is instituted when the disorder is caused by a magnesium deficiency. ○ Parathyroid hormone is not currently available commercially. ○ Calcium and vitamin D are the mainstays of treatment to correct hypocalcemia. ○ Intravenous calcium gluconate is often given slowly until tetany remits. ○ Oral calcium can be given as calcium carbonate or calcium citrate. ○ Vitamin D therapy should be started as soon as calcium therapy begins. ○ The treatment of choice is ergocalciferol because it is slow-acting and produces a stable calcium level. ○ Vitamin D preparations act by promoting the release of calcium from bone into blood and stimulating the absorption of both calcium and phosphate from the small intestine. ○ Other vitamin D preparations include: dihydrotachysterol (which is faster in onset and three times more potent than ergocalciferol but also more expensive) Calciferol (which has an intermediate onset and duration of action) Calcitriol (which is very expensive but also has a rapid onset of action)