Hypoparathyroidism Flashcards
What is hypoparathyroidism?
Hypoparathyroidism is a condition characterised by low parathyroid hormone (PTH) levels, leading to hypocalcaemia and hyperphosphataemia.
What are the common causes of hypoparathyroidism?
Post-surgical damage or removal of the parathyroid glands, autoimmune destruction, genetic disorders, or infiltrative diseases.
What is the most common cause of hypoparathyroidism?
Post-surgical hypoparathyroidism, often following thyroid or parathyroid surgery.
What is the role of PTH in calcium regulation?
PTH increases blood calcium levels by stimulating bone resorption, increasing renal calcium reabsorption, and enhancing calcium absorption in the gut via vitamin D.
What are the symptoms of hypoparathyroidism?
Muscle cramps, paraesthesia, tetany, fatigue, irritability, and in severe cases, seizures or cardiac arrhythmias.
What are the signs of hypocalcaemia seen in hypoparathyroidism?
Positive Chvostek’s sign, positive Trousseau’s sign, muscle twitching, and carpopedal spasms.
What is Chvostek’s sign?
A twitching of the facial muscles when the facial nerve is tapped, indicating hypocalcaemia.
What is Trousseau’s sign?
Carpopedal spasm induced by inflating a blood pressure cuff, indicative of hypocalcaemia.
How does hypoparathyroidism affect serum calcium and phosphate levels?
Serum calcium is low (hypocalcaemia), and phosphate levels are high (hyperphosphataemia).
What are the typical biochemical findings in hypoparathyroidism?
Low serum calcium, high serum phosphate, and low or inappropriately normal PTH levels.
How is vitamin D involved in hypoparathyroidism?
PTH deficiency reduces renal conversion of inactive vitamin D to active 1,25-dihydroxyvitamin D, impairing calcium absorption in the gut.
What are the causes of post-surgical hypoparathyroidism?
Accidental removal or damage to the parathyroid glands during thyroidectomy or parathyroidectomy.
What is pseudohypoparathyroidism?
A condition where there is resistance to PTH action, leading to hypocalcaemia and hyperphosphataemia, despite normal or elevated PTH levels.
What investigations are used to diagnose hypoparathyroidism?
Serum calcium, phosphate, PTH levels, renal function tests, magnesium levels, and potentially genetic testing in suspected hereditary cases.
What imaging studies can be used in hypoparathyroidism?
Dual-energy X-ray absorptiometry (DEXA) to assess bone density and, in some cases, brain imaging to check for basal ganglia calcifications.
What is the first-line treatment for chronic hypoparathyroidism?
Calcium and active vitamin D supplementation (e.g., calcitriol).
How is acute symptomatic hypocalcaemia managed?
Intravenous calcium gluconate is given to rapidly correct severe hypocalcaemia.
What is the role of magnesium in hypoparathyroidism?
Hypomagnesaemia can impair PTH secretion and function, so correcting magnesium levels is essential in hypoparathyroidism management.
What dietary advice should be given to patients with hypoparathyroidism?
Maintain adequate dietary calcium intake and avoid foods high in phosphate, such as fizzy drinks and processed meats.
What are the complications of untreated hypoparathyroidism?
Seizures, cardiac arrhythmias, cataracts, and calcifications in the basal ganglia or other soft tissues.
How does hypoparathyroidism affect bone health?
Unlike hyperparathyroidism, hypoparathyroidism does not cause bone resorption but may lead to increased bone density.
What is the role of recombinant human PTH (rhPTH) in hypoparathyroidism?
It is used in selected patients with chronic hypoparathyroidism who are unresponsive to conventional therapy.
What are the symptoms of hyperphosphataemia in hypoparathyroidism?
Symptoms include pruritus, soft tissue calcifications, and in severe cases, hypocalcaemia symptoms due to phosphate binding calcium.
What is the role of thiazide diuretics in hypoparathyroidism management?
Thiazide diuretics can reduce urinary calcium excretion, potentially reducing the risk of nephrolithiasis in some patients.
What is the prognosis for patients with hypoparathyroidism?
With appropriate management, most patients have a good quality of life, although some may experience persistent symptoms or complications.
