T1 L4 & 5 Calcium homeostasis Flashcards
What can cause too much hormone to be produced?
Single nodule
Multiple nodules
Generalised increase in tissue (hyperplasia)
What are the layers of the adrenal glands?
Zona glomerulosa
Zona fasciculata
Zona reticularis
Medulla
What is primary hyperaldosteronism?
Conn’s syndrome
Excess production of hormone aldosterone from the adrenal glands which leads to low renin levels
Occurs in zona glomerulosa
What are the adrenal causes of hypertension?
Primary hyperaldosteronism
Phaeochromocytoma
What are the causes of too much aldosterone in the zona glomerulosa?
Adenoma
Hyperplasia
Rare genetic causes
What hypertensive patients should be screened?
Hypokalaemia
Resistant hypertension
Younger people
What tests can be used to diagnose primary hyperaldosteronism?
Initial screening tests: suppressed renin, normal / high aldosterone
Confirmatory tests: oral or Iv sodium suppression test
What tests can be done to find the cause of primary hyperaldosteronism?
Adrenal CT scan
Adrenal venous sampling
Metomidate PET CT
What treatment is given for unilateral adenoma?
Laparoscopic adrenalectomy
Medical treatment
What treatment is given for bilateral hyperplasia?
Medical treatment (aldosterone antagonists) Spironolactone Eplerinone
What does phaeochromocytoma cause?
Increased adrenaline and noradrenaline leading to raised BP
What catecholamines does the adrenal medulla produce?
Dopamine
Norepinephrine
Epinephrine
How does phaeochromocytoma present?
Spells of headache, sweating, pallor, palpitation, anxiety
Hypertension (permanent or intermittent)
What genetic conditions are associated with phaeochromocytoma?
Neurofibromatosis type 1 (NF1)
Multiple endocrine neoplasia type 2 (MEN 2)
Von Hippel-Lindau syndrome
What is the biochemical diagnosis for phaeochromocytoma?
24 hour urine: normetanephrines and metanephrines will be high. 3 methoxytyromine
Plasma: noradrenalin, adrenalin and metanephrines
Why can’t you measure urine dopamine when diagnosing phaeochromocytoma?
This comes from the kidney and the nervous system and not from the adrenal medulla
What are some other causes of raised catecholamines?
Obstructive sleep apnoea
Amphetamine like drugs
L-DOPA
Labetalol
What is the management of phaemochromocytoma?
Alpha blockers
Beta blockers
Laparoscopic adrenalectomy
What are the effects of noradrenaline?
Vasoconstriction leading to increased BP and pallor
Glycogenolysis
What are the effects of adrenaline?
Vasoconstriction
Vasodilation in muscle
Increased heart rate
Sweating
Why does hypocalcaemia destabilise neurons?
1) Decrease in extracellular calcium concentration
2) Increased membrane permeability to sodium
3) Sodium depolarises membrane
4) Action potential
What are the physical signs of hypocalcaemia?
Carpopedal spasm
Chvostek’s sign
What is carpopedal spasm?
Occlude brachial artery using BP cuff causes a carpal spasm
What is Chvostek’s sign?
Abnormal reaction to stimulation of facial nerve
Tap facial nerve at angle of jaw causes facial muscles on same side to contract
What are the acute consequences of hypercalcaemia
Thirst and polyuria
Abdominal pain
What are the chronic consequences of hypercalcaemia?
Constipation Musculoskeletal aches / weakness Neurobehavioural symptoms Renal calculi Osteoporosis
How much calcium is protein bound?
40%
Albumin bound - 90%
Globulin bound - 10%
How much calcium is bound to cations?
10%
How much calcium is ionised?
50%
What can make the corrected calcium inaccurate?
Albumin concentration below 20g/l
Severe acute illness
What are the normal levels of calcium in the blood?
2.15-2.55mmoles/l
What does activation of calcium-sensing receptor cause?
Activation of phospholipase C leading to DAG & IP3
Inhibition of adenylate cyclase which suppresses intracellular concentration of cAMP
Can activate mitogen-activated protein kinase pathway
What is primary hyperparathyroidism?
Body has too much parathyroid hormone
What are the symptoms of primary hyperparathyroidism
Fatigue Fractures Decreased height Upper abdominal pain Loss of appetite Nausea Muscle pain Depression Kidney stones
What test results diagnose primary hyperparathyroidism?
Raised serum calcium
Lowered serum phosphate
Raised PTH
Bone X-ray may show bone reabsorption or fractures
Imaging of kidneys or ureters may show calcification or blockage
What is the treatment for primary hyperparathyroidism?
Drinking more fluids to prevent kidney stones
Avoiding immobilisation
Avoiding thiazide-like diuretics
What are the complications of primary hyperparathyroidism?
Osteoporosis
Bone cysts if severe
What are the causes of hypoparathyroidism?
Iatrogenic - thyroidectomy, radical neck surgery
Autoimmune
Hypomagnesaemia
Genetic mutations
What are some common causes of secondary hyperparathyroidism?
Low / low normal serum calcium and hight PTH
Low serum 25 OH vitamin D (lack of sun exposure, GI problems)
Renal failure
