Parathyroid Flashcards
What does Parathyroid Hormone (PTH) affect?
Calcium - increase
Phosphate - decrease
What controls PTH?
Calcium ions decrease
What does calcitonin affect?
Calcium - decrease
Phosphate - decrease
What do vitamin D metabolites affect?
Calcium - increase
Phosphate - increase
What controls calcitonin?
Calcium ions increase
Gastrin
What controls vitamin D metabolites?
Phosphate decrease
PTH increase
Which cells secrete PTH?
Chief cells of the parathyroid gland
What receptor activates the cells for secretion of PTH?
Calcium sensing receptor on chief cells
How does PTH work on chief cell receptors?
Enhances:
- renal tubular calcium reabsorption
- osteoclast mediated bone resorption
- conversion of 25(OH) vit D to 1,25(OH) vit D3
Describe the relationship between PTH and plasma calcium.
PTH level at highest when plasma Calcium at lowest
PTH level at lowest when plasma Calcium at highest
What are the most common causes of hypercalcaemia?
- Primary hyperparathyroidism
- Malignancy
What are some less common causes of hypercalcaemia?
- Milk-alkali syndrome
- Ingestion of foods containing Vitamin D, including cod liver oil/herbal medication
- Granulomatous diseases, sarcoidosis
- Thiazide diuretics
- Familial benign hypocalciuric hypercalcemia
Rare causes of hypercalcaemia?
- Lithium
- Total parenteral nutrition
- Oestrogens/antioestrogens, testosterone
- Vitamin A toxicity
- Foscarnet
- Thyrotoxicosis
- Pheochromocytoma
- Adrenal insufficiency
- Vasoactive intestinal polypeptide hormone producing tumours
- Immobilisation
How does excess PTH affect serum?
Increased calcium Decreased phosphorus Increased alkaline phosphatase Increased Chloride Decreased bicarbonate Increased PTH
How does excess PTH affect urine?
Increased calcium
Increased phosphorous
Increased cyclic AMP
Define:
- Primary hyperparathyroidism
- Secondary hyperparathyroidism
- Tertiary hyperparathyroidism
Primary hyperparathyroidism:
- Adenoma, hyperplasia, carcinoma
Secondary hyperparathyroidism:
- Compensatory, elevated PTH level secondary to hypocalcaemia with parathyroid gland hyperplasia
Tertiary hyperparathyroidism:
- Autonomous secretion of PTH following
longterm hypocalcaemia
What are the symptoms of hypercalcaemia?
“Stones, moans, (abdo) groans, and bones”
- Renal stones
- Depression, confusion, tiredness
- Muscle weakness + GI pain inc. anorexia, PUD, pancreatitis
- Bone pain and osteoporosis
- Polydipsia and polyuria
- Arrythmias, corneal calcification
What investigations are done for hypercalcaemia?
Bloods:
- ↑ Ca2+, ↓ (PO4)2-
- ↑ ESR and hypercalcaemia => myeloma
- PTH levels: ↑ in hyperparathyroidism, ↓ otherwise
DEXA bone scan
How is primary hyperparathyroidism treated?
Surgical excision - of adenoma or all 4 glands in hyperplasia
What are the causes of hypocalcaemia?
With high (P04)2- :
- hypoparathyroidism
[] primary = usually autoimmune
[] pseudo = failure of receptor response to PTH, may be caused by hypomagnesaemia
[] secondary = surgery/radiation of PT glands - vitamin D deficiency
- Chronic renal failure
[] due to ↓ vit D synth and ↑PO4 => ↓ GI absorption of Ca2+
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With normal/low (P04)2- :
- Osteomalacia = decreased dietary intake, malabsorption
- Pancreatitis
- Alkalosis = total Ca2+ levels may be normal, but ionised will be reduced
What are the symptoms of hypocalcaemia?
Anxiety Confusion Nervous irritability/tetany - fasciculations and spasms - hyperreflexia - convulsions Paraesthesia ECG = prolonged ST segment and QT interval
What are the symptoms of chronic hypocalcaemia?
Osteomalacia
Diarrhoea
What are the signs of hypocalcaemia?
Chvostek’s sign - tapping the facial nerve cause brief ipsilateral facial spasm
Trousseau’s sign - arm spasm occurs after 1-4 mins of inflated BP cuff ~20mmHg
What investigations should be done to diagnose hypocalcaemia?
Ca2+ an (PO4)2- levels
PTH levels
Parathyroid antibody levels
How should hypocalcaemia be managed?
If acute/severe then:
- calcium gluconate by IV infusion
- check and correct hypomagnesaemia
- check and correct alkalosis
If hypoparathyriodism/pseudohypoparathyroidism then:
- Vitamin D supplementation
