Parathyroid Disorders Flashcards
what do the parathyroid glands secrete?
in response to what?
secrete PTH from chief cells in response to low calcium
what does PTH do
Increases serum calcium
how does PTH increase serum calcium
- Increases osteoclast activity – reabsorption of calcium from bone
- increases calcium reabsorption in the kidney – decreased calcium excreted in urine
- stimulates kidneys to convert vit D3 to calcitriol (active form of Vit D) – increases calcium absorption form small intestine
causes of hypercalcaemia
hyperparathyroidism
bone metastasis
sarcoidosis
myeloma
ECG hypercalcaemia
short QT interval
symptoms of hypercalcaemia
“Bones stones groans + moans”
- painful bones +/- fractures
- renal stones
- abdominal pain / constipation
- depression / confusion
also:polydipsia, polyuria, dehydration
what is primary hyperparathyroidism
excess PTH production by parathyroid causing hypercalcaemia
most common cause of primary hyperparathyroidism
solitary adenoma (85%)
- hyperplasia (15%)
- carcinoma (<1%)
blood results primary hyperparathyroidism
increased calcium
increased/normal PTH
low phosphate
increased ALP
treatment of adenoma causing primary hyperparathyroidism
surgery
general management of high calcium
IV fluids
Loop diuretics
Treat underlying cause
what is secondary hyperparathyroidism
increased PTH in response to hypocalcaemia
what causes secondary hyperparathyroidism
Chronic renal failure
Vit D deficiency
Low calcium in diet
– low absorption of calcium from intestines bones kidneys
blood results secondary hyperparathyroidism
low calcium
high PTH
high phosphate
high ALP
Treatment of secondary hyperparathyroidism
alfacalcidiol
what is tertiary hyperparathyroidism
due to longstanding secondary hyperparathyroidism
- PTH production remains high despite increased calcium levels
blood results tertiary hyperparathyroidism
high calcium
high PTH
high phosphate
high ALP
treatment of tertiary hyperparathyroidism
surgical removal of hyperplasia
what is malignant hyperparathyroidism
parathyroid related protein (PTHrP) is produced by malignant squamous cell carcinomas elsewhere in body and mimics PTH
what cancers cause malignant hyperparathyroidism
squamous cell lung cancer
breast cancer
renal cancer
blood results malignant hyperparathyroidism
decreased PTH
increased calcium
increased phosphate
hypocalcaemia changes on ECG
prolonged QT interval
what is chvostek’s sign
tapping over facial nerve causes twitching of facial muscles in patients with hypocalcaemia
what is trousseau’s sign
inflation of BP cough above systolic BP causes hand spasm in patients with hypocalcaemia
symptoms of hypocalcaemia
muscle aches
tetany - muscle spasms
pins + needles
what is primary hypoparathyroidism
decreased PTH secretion
most common cause of primary hypoparathyroidism
damage/accidental removal of glands secondary to thyroid surgery
bloods in primary hypoparathyroidism
low PTH
low calcium
high phosphate
treatment of primary hypoparathyroidism
calcium + vit D supplements
what is pseudohypoparathyroidism
cells are resistant to PTH
- Abnormality in a G protein
features of pseudohypoparathyroidism
low IQ
short metacarpals + short metatarsals
short stature
pixie face
bloods in pseudohypoparathyroidism
high PTH
low calcium
high phosphate
how is diagnosis of pseudohypoparathyroidism made
measuring urinary cAMP + phosphate levels following PTH infusion
- both will rise in hypoparathyroid
- neither will rise in pseudohypoparathyroid
what is pseudopseudohypoparathyroidism
same feature of pseudohypoparathyroid but normal blood biochemistry
