Hypoparathyroidism

Hypoparathyroidism is a rare endocrine condition characterised by decreased function of the parathyroid glands, resulting in underproduction of parathyroid hormone (PTH). The deficiency in PTH leads to hypocalcaemia, which can cause muscle cramps, twitching, and tetany. This condition can be inherited or acquired, often following thyroid or parathyroid gland surgery or due to autoimmune damage.

Signs and Symptoms

The primary symptoms of hypoparathyroidism are related to low blood calcium levels, which interfere with normal muscle contraction and nerve conduction. Common symptoms include:

• Paresthesia: An unpleasant tingling sensation around the mouth and in the hands and feet.
• Muscle cramps and severe spasms (tetany) affecting hands and feet.
• Fatigue, headaches, bone pain, and insomnia.
• Crampy abdominal pain.

During physical examination, tetany might be observed. Specific signs include Chvostek's sign (twitching of facial muscles when the facial nerve is tapped) and Trousseau's sign (carpal spasm induced by inflating a blood pressure cuff). Severe hypocalcaemia can lead to medical emergencies such as seizures, irregular heartbeats, and respiratory failure due to airway spasms.

Causes

Hypoparathyroidism can result from various causes:

• Surgical: Removal or trauma to the parathyroid glands during thyroid or parathyroid surgery is the most common cause.
• Autoimmune: Part of autoimmune polyendocrine syndromes.
• Genetic: Conditions like DiGeorge syndrome and Kenny-Caffey syndrome.
• Other: Magnesium deficiency, haemochromatosis, and idiopathic causes.

Mechanism

The parathyroid glands, usually located behind the thyroid gland, contain chief cells that sense blood calcium levels and secrete PTH. PTH regulates calcium and phosphorus levels by acting on the kidneys, bones, and intestines. It increases calcium reabsorption in the kidneys, enhances calcium and phosphorus absorption in the intestines via vitamin D, and stimulates bone resorption to release calcium and phosphorus into the blood.

Diagnosis

Diagnosis involves measuring blood calcium, serum albumin, and PTH levels. Differential diagnoses include pseudohypoparathyroidism, vitamin D deficiency, malabsorption, kidney disease, and certain medications. Additional tests like ECG and blood magnesium levels may be necessary.

Treatment

Acute Management

Severe hypocalcaemia, a life-threatening condition, is treated with intravenous calcium (e.g., calcium gluconate) and precautions to prevent seizures and larynx spasms. The heart is monitored for abnormal rhythms during treatment.

Long-term Management

Long-term treatment includes vitamin D analogues (calcitriol or alfacalcidol), vitamin D supplementation, and calcium supplementation. Regular monitoring of blood and urine calcium levels is essential to avoid complications like hypercalcaemia and hypercalciuria, which can lead to nephrocalcinosis and chronic kidney disease.

Recombinant human parathyroid hormone (PTH) and teriparatide (PTH 1-34) are second-line therapies for patients unresponsive to conventional treatment. These medications are administered via subcutaneous injections and must be tapered off gradually to prevent bone demineralisation.

Monitoring

Periodic kidney ultrasounds may be considered to assess for nephrocalcinosis in patients on long-term therapy for hypoparathyroidism.

A 2019 systematic review indicated a lack of high-quality evidence for the use of vitamin D, calcium, or recombinant parathyroid hormone in managing hypoparathyroidism post-thyroidectomy.

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Self-assessment MCQs (single best answer)

What is the primary hormone deficient in hypoparathyroidism?

Which symptom is most directly related to hypocalcaemia in hypoparathyroidism?

Chvostek's sign is indicative of:

Which of the following is a common cause of acquired hypoparathyroidism?

What is the first-line treatment for life-threatening hypocalcaemia?

Which condition is NOT typically associated with hypoparathyroidism?

What is the role of parathyroid hormone (PTH)?

Long-term management of hypoparathyroidism often includes:

What is Trousseau's sign?

Which monitoring method is important for patients on long-term hypoparathyroidism therapy?