Hyperparathyroidism + Hypoparathyroidism + Diabetes Insipidus Flashcards
Physiology of the parathyroid glands
There are four parathyroid glands situated in four corners of the thyroid gland. The parathyroid glands, particularly the chief cells in the glands, produce parathyroid hormone in response to hypocalceaima.
How does parathyroid hormone act to raise blood calcium levels?
- Increases osteoclast activity in bones
- Increases calcium absorption from gut
- Increases calcium absorption from kidneys
- Converts vitamin D into active forms, vitamin D increases calcium absorption from intestines
Symptoms of hypercalcaemia
Renal stones, painful bones, abdominal groans and psychiatric moans.
- Renal stones
- Painful bones
- Abdominal groans refers to symptoms of constipation, nausea and vominting
- Psychiatric moans refers to symptoms of fatigue, depression and psychosis
Pathophysiology of primary hyperparathyroidism
Primary hyperparathyroidism is caused by uncontrolled parathyroid hormone produced directly by a tumour of the parathyroid glands. This leads hypercalcaemia.
Management of primary hyperparathyroidism
Surgical removal of the tumour
Pathophysiology of secondary hyperparathyroidism
Insufficient vitamin D or chronic renal failure leads to low absorption of calcium, resulting in hypocalcaemia.
Parathyroid hyperplasia occurs. Parathyroid hormone will be high.
Management of secondary hyperparathyroidism
Correct vitamin D deficiency or perform renal transplantation to treat renal failure.
Pathophysiology of tertiary hyperparathyroidism
This happens when secondary hyperparathyroidism continues for a long period of time.
It leads to hyperplasia of the glands and increased parathyroid hormone levels.
When the cause of the secondary hyperparathyroidism is treated the parathyroid hormone level remains inappropriately high leading to hypercalaemia.
Management of tertiary hyperparathyroidism
Surgical removal of part of the thyroid tissue
Cause of hypoparathyroidism
Iatrogenic: neck surgery or radiation (the vast majority)
Clinical features of hypoparathyroidism
Hypocalacemia
- Muscle twitching
- Lethargy
- Muscle spasma
- Psychosocial changes
- Prolonged QT interval
- Chovostek sign: twitching of the facial muscles on tapping the cheek
- Trousseau sign: spasm of the muscles of the hand on application of a BP cuff (rare)
Describe pseudohypoparathyroidism
Hypocalcaemia is present but PTH is elevated, primarily because of end organ receptor insensitivity to the effect of PTH.
Investigations for hypoparathyroidism
- Decreased serum calcium
- Elevated phosphate
- Decreased PTH
- Normal alkaline phosphatase (ALP)
Management of hypoparathyroidism
- Severe hypocalcaemia
- IV calcium gluconate is indicated
- Long term management
- Calcium and vitamin D replacement
What is the role of anti diuretic hormone?
Pathophysiology of diabetes insipidus?
ADH acts on the collecting ducts in the kidneys, allowing them to reabsorb water from the urine.
Diabetes insipidus prevents kidneys from concentrating urine resulting in polydipsia and polyuria.
