Hyperparathyroidism and Hypoparathyroidism
Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management
Definition
Disorders of the parathyroid refer to conditions that disrupt parathyroid hormone (PTH) regulation, affecting calcium homeostasis. The main disorders include hyperparathyroidism and hypoparathyroidism.
Aetiology
- Primary hyperparathyroidism: most commonly due to parathyroid adenoma, less commonly due to parathyroid hyperplasia or carcinoma.
- Secondary hyperparathyroidism: occurs due to chronic hypocalcaemia from chronic kidney disease, vitamin D deficiency, or malabsorption.
- Tertiary hyperparathyroidism: persistent hyperparathyroidism after prolonged secondary hyperparathyroidism, often in end-stage renal disease.
- Hypoparathyroidism: can be due to surgical removal of the parathyroid glands, autoimmune disease, or genetic disorders (e.g., DiGeorge syndrome).
Pathophysiology
- Parathyroid hormone (PTH) regulates calcium and phosphate balance by acting on bones, kidneys, and the intestines.
- Hyperparathyroidism results in increased calcium resorption from bone, increased renal calcium reabsorption, and enhanced intestinal calcium absorption.
- Hypoparathyroidism leads to decreased calcium levels due to reduced PTH activity, impairing bone resorption and renal calcium reabsorption.
Risk Factors
- Family history of parathyroid disorders.
- Chronic kidney disease (risk for secondary hyperparathyroidism).
- Prior neck surgery or radiation exposure.
- Vitamin D deficiency.
- Genetic syndromes (e.g., MEN1, MEN2A).
Signs and Symptoms
- Hyperparathyroidism:
- Hypercalcaemia symptoms: fatigue, polyuria, nephrolithiasis, bone pain, abdominal pain.
- Osteoporosis due to increased bone resorption.
- Neuropsychiatric symptoms: depression, confusion, weakness.
- Hypoparathyroidism:
- Hypocalcaemia symptoms: muscle cramps, paraesthesia, tetany.
- Chvostek’s and Trousseau’s signs (indicative of neuromuscular irritability).
- Seizures or cardiac arrhythmias in severe cases.
Investigations
- Serum calcium and phosphate: hypercalcaemia in hyperparathyroidism, hypocalcaemia in hypoparathyroidism.
- PTH levels: elevated in primary and secondary hyperparathyroidism, low in hypoparathyroidism.
- Vitamin D levels: to assess for secondary causes of parathyroid dysfunction.
- Renal function tests: to evaluate for secondary hyperparathyroidism due to chronic kidney disease.
- DEXA scan: to assess bone mineral density in hyperparathyroidism.
- Neck ultrasound: to localise parathyroid adenomas.
Management
1. Hyperparathyroidism:
- Parathyroidectomy: indicated for symptomatic primary hyperparathyroidism or complications such as osteoporosis or nephrolithiasis.
- Medical management: calcimimetics (e.g., cinacalcet) for secondary or tertiary hyperparathyroidism, bisphosphonates for bone protection.
2. Hypoparathyroidism:
- Calcium and vitamin D supplementation: lifelong treatment to maintain normal calcium levels.
- Recombinant PTH therapy: reserved for severe or refractory cases.
3. Referral:
- Endocrinology: for long-term management of parathyroid disorders.
- Nephrology: if associated with chronic kidney disease and secondary hyperparathyroidism.
- Surgery: for evaluation of parathyroidectomy in eligible cases.