Hyper & Hypoparathyroidism Flashcards
How many parathyroid glands are there? Where are they located?
4 parathyroid glands, situated in 4 corners of the thyroid gland.
What is the role of the parathyroid glands?
Chief cells of parathyroid glands produce PTH in response to hypocalcaemia.
Via what 3 ways does PTH increase calcium levels?
1) Increasing osteoclast activity in bones (reabsorbing calcium from bones)
2) Increasing calcium reabsorption in the kidneys (less calcium is lost in urine)
3) Increasing vitamin D activity (converts it into its active form), resulting in increased calcium absorption in the intestines
Vitamin D & calcium?
Vitamin D acts to increase calcium absorption from the intestines.
What is the most common cause of hypercalcaemia in outpatients?
1ary hyperparathyroidism
1ary vs 2ary hyperparathyroidism?
1ary –> caused by uncontrolled PTH production by a tumour of the parathyroid gland.
2ary –> insufficient vitamin D or CKD reduces calcium absorption from the intestines, kidneys and bones –> hypocalcaemia –> raised PTH
What is 3ary hyperparathyroidism?
When 2ary hyperparathyroidism continues for an extended period, after which the underlying cause is treated.
Hyperplasia of the parathyroid glands occurs as they adapt to producing a higher baseline level of PTH.
When the underlying cause of the secondary hyperparathyroidism is treated, the baseline parathyroid hormone production remains inappropriately high.
What is the most common cause of 1ary hyperparathyroidism?
Solitary parathyroid adenoma
What inherited condition can cause 1ary hyperparathyroidism?
Multiple endocrine neoplasia (MEN)
What happens in the 1ary hyperparathyroidism?
A region of cells within the parathyroid glands cease to respond to this negative feedback loop.
These cells continuously secrete PTH irrespective of the serum calcium concentration.
This results in hypercalcaemia.
Symptoms of hypercalcaemia?
‘Stones’ - increased risk of kidney stones
‘Bones’:
- Bone pain
- Osteopenia and osteoporosis
‘Abdo groans’:
- Abdominal pain
- Constipation
- N&V
‘Psychiatric moans’
- Fatigue
- Depression
- Memory impairment
Also polyuria, paraesthesia & muscle cramps.
What should be excluded in all patients with hypercalcaemia?
Malignancy
What are the 2 main mechanisms of hypercalcaemia of malignancy?
1) PTHrP secreting tumours (e.g. lung, breast and kidney)
2) Osteolytic lesions (e.g. bone metastasis and multiple myeloma)
Serum PTH in hypercalcaemia of malignancy?
Low
What is familial hypocalciuric hypercalcaemia (FHH)?
A rare autosomal domination condition in which there is reduced renal excretion of calcium
What test can be used to differentiate between hyperparathyroidism & FHH?
24-hour urinary calcium:
- FHH results in a hypocalciuria
- 1ary hyperparathyroidism results in high or normal urinary calcium
Interpret results:
- High PTH
- High calcium
1ary hyperparathyroidism –> tumour
OR
3ary hyperparathyroidism –> hyperplasia
Interpret results:
- High PTH
- Low/normal calcium
2ary hyperparathyroidism –> Low vitamin D or CKD
Most common 1st line mx of 1ary hyperparathyroidism?
Parathyroidectomy
If surgery is not possible, what are some mx options for symptomatic hypercalcaemia in 1ary hyperparathyroidism?
1) Calcitonin
2) Cinacalcet
3) Bisphosphonates
How does calcitonin reduce serum calcium levels?
By inhibiting bone and kidney resorption of calcium
What are some complications of untreated hypercalcaemia?
1) Osteoporosis and fragility fractures
2) Kidney stones and kidney injury
3) HTN & heart disease
4) GI disorders e.g. peptic ulcer disease, pancreatitis and gallstones
What are some procedure specific complications that can arise following a parathyroidectomy? (2)
1) Damage to the recurrent or superior laryngeal nerves
2) Post operative hypocalcaemia can result after the removal of too much parathyroid tissue
How does increased PTH affect phosphate?
Causes LOW phosphate levels
What is hypoparathyroidism?
Deficient or absent PTH production –> low levels of calcium and high levels of phosphate in the blood.
What is the most common cause of hypoparathyroidism?
Damage or removal of the parathyroid glands during neck surgery, especially thyroidectomy.
What genetic disorder can result in hypoparathyroidism?
DiGeorge syndrome
What is the hallmark feature of hypoparathyroidism?
Hypocalcaemia –> presents with neuromuscular irritability
- mild numbness or tingling of the extremities and around the mouth
- muscle cramps
- fatigue
- tetany
- carpopedal spasm
- laryngospasm
- seizures
What 2 signs may be elicited in hypocalcaemia?
1) Chvostek’s sign
2) Trousseau’s sign
What is Trousseau’s sign?
carpopedal spasm induced by occluding the brachial artery with a blood pressure cuff
What is Chvostek’s sign?
Twitching of the facial muscles in response to tapping over the facial nerve
What may ECG show in hypocalcaemia?
Prolonged QT interval
Mx of hypoparathyroidism?
1) Oral calcium & active vitamin D analogues e.g. calcitriol or alfacalcidol
2) Diet - high-calcium, low-phosphorus diet
