Endocrinology: Passmed Flashcards
Which electrolyte is important for parathyroid secretion?
Magnesium, which also mediates the action of PTH on target tissue. Reduction in magnesium can lead to hypocalcaemia, which is unresponsive to treatment with supplementation.
What is the role of prolactin?
Stimulates milk production and breast development and inhibits gonadal activity.
What is the primary hyperparathyroidism?
Typically caused by solitary adenoma and parathyroid carcinoma, characterised by:
-> High PTH and calcium
-> Low phosphate and low urine calcium and creatinine
What is the cause of secondary hyperparathyroidism?
Parathyroid gland hyperplasia due to low calcium, associated chronic renal failure. It is characterised by:
-> High PTH and phosphate
-> Low calcium and Vitamin D
What is tertiary hyperparathyroidism?
Hyperplasia of the thyroid gland after correction of the parathyroid glands, with hyperplasia of all 4 glands. It is characterised by:
High PTH and calcium and ALP
Decreased phosphate and Vitamin D
What is the cause of congenital adrenal hyperplasia?
Deficiency in 21-hydroxylase enzyme, which is important for the production of cortisol and aldosterone, but there is excess production of androgens. There is virilisation of the female genitalia, with precocious (early) puberty in males
How does insulin affect electrolytes?
Hypokalemia and hypernatremia due to increased activity of the sodium-potassium pump. It inhibits lipolysis and reduces muscle protein loss.
What happens to urine osmolality during a water deprivation test in healthy individuals?
Plasma osmolality begins low
Urine osmolality ends high
Urine osmolality remains high following administration of ADH.
-> High urine osmolality occurs in water deprivation due to ADH stimulating water and salt reabsorption. Final high urine osmolality indicates preserved kidney tubule function.
What happens to urine osmolality during a water deprivation test in patients with cranial diabetes insipidus?
Starting plasma osmolality is high
Final urine osmolality is low
Following administration of ADH, urine osmolality will be high
Deficiency of ADH causes excessive loss of water, therefore administration of synthetic ADH will correct this. Plasma osmolality is high due to dehydration.
What happens to urine osmolality during a water deprivation test in nephrogenic diabetes insipidus?
Plasma osmolality will be high
Final Urine osmolality will be low
Administration of ADH will cause final urine osmolality to be unchanged and remain low
-> This will occur due to reduced kidney tubule function reducing the ADH activity
How does PTH act?
Increases the activity of the 1-alpha-hydroxylase ENZYME for the activation of Vitamin D from 1,25 hydroxycholecalciferol for increased reabsorption of calcium from the small intestine.
What are the symptoms associated with excess glucorticoids?
Thinning of the skin
Osteonecrosis and osteoporosis
Sodium and water retention, causing hypernatremia and hypokalemia
Growth retardation in children
What is the action of cortisol?
Anti-inflammatory effects
Skeletal muscle breakdown
Stimulation of lipoplysis
Mineralcorticoid effects
What are the features of DKA?
Excessive uncontrolled lipolysis which results in accumulation of fatty acids, which causes nausea, vomiting, fruity-smelling breath and dehydration. This is triggered by infection or surgery. There is increased gluconeogenesis, with Kussmaul breathing and polyuria and polydipsia.
What is used for a differential diagnosis in primary aldosteronism?
Adrenal vein sampling, which can be used to differentiate between unilateral and bilateral adrenal hyperplasia, to take a blood sample and testing for hormone levels
