Endocrine Mix Flashcards
function of PTH in bone?
binds to osteoblasts which activates osteoclasts triggering bone resorption and release of calcium
function of PTH in kidneys?
increases reabsorption of calcium and magnesium in the distal convoluted tubule
decreases reabsorption of phosphate
function of PTH in gut?
increases gut absorption of calcium by activating Vitamin D
what cells secrete PTH?
chief cell in parathyroid glands
what drives growth in each stage of growth?
infancy (birth - 2yrs) = nutrition and insulin
childhood (2-11) = GH and thyroxine
puberty (12-18) = sex hormones and GH
features of primary hyperaldosteronism?
hypertension
muscle weakness (due to low potassium)
hypokalaemia
alkalosis
how is primary hyperaldosteronism investigated?
aldosterone : renin ratio = first line
- will be high
CT scan and adrenal vein sampling
how is primary hyperaldosteronism managed?
adrenal adenoma = adrenalectomy
bilateral adrenocortical hyperplasia = aldosterone antagonist (spironolactone)
what is cholesterol converted to in the formation of steroid hormones?
pregnenalone
what is waterhouse freidrichson syndrome?
adrenal gland failure due to a previous bleed in the adrenal gland as a result of a bacterial infection
most common cause = Neisseria meningitides
how can increased exercise affect blood sugar in diabetes?
causes early and late decrease in blood sugar due to uptake of glucose in muscles
what is congenital adrenal hyperplasia?
group of autosomal recessive disorders causing defects in enzymes involved in conversion of cholesterol to mineralocorticoids, glucocorticoids and sex steroids
how does hyperplasia occur in CAH?
low cortisol > increased ACTH > stimulation of steroid producing cells > hyperplasia to try and accommodate for loss of function
what is the most common cause of CAH and how does it present?
21 hydroxylase deficiency
- virilisation of female genitalia
- precocious puberty in males
- most have a salt losing crisis at 1-3 weeks old
name 2 other causes of CAH and how do they differ from 21 hydroxylase deficiency?
11-beta hydroxylase deficiency - same apart from also has hypertension and hyperkalaemia 17 hydroxylase deficiency - non-virilising in females - intersex in males - causes hypertension
what is Conn’s syndrome and what are the 2 main causes?
primary hyperaldosteronism
- adrenal adenoma
- diffuse/nodular hyperplasia of both adrenals
triad of features in conns syndrome?
hypertension
alkalosis
hypokalaemia
how can conns syndrome be distinguished from renal artery stenosis?
conns = low renin RAS = high renin
name 2 causes of acute adrenocortical hypofunction
rapid withdrawal of steroid medication
massive adrenal haemorrhage
what can cause chronic adrenocortical hypofunction?
autoimmune adrenalitis infection metastatic malignancy anti-phospholipid syndrome rare - sarcoidosis, amyloidosis, haemochromatosis
symptoms of addisons disease only occur after what percentage of adrenal function is lost?
90%
what are the symptoms of addisons disease?
weakness and fatigue vomiting weight loss diarrhoea pigmentation of skin/mucosal membranes (esp in creases) hypotension (due to lack of aldosterone)
what biochemistry is found in addisons disease?
hyponatraemia
hyperkalaemia
low aldosterone
hypoglycaemia (due to reduced glucocorticoids - cortisol induced gluconeogenesis)
what is addisonian crisis and how does it present?
medical emergency of severe adrenal insufficiency hypovolaemic shock fever abdominal pain vomiting convulsions shock death
most common presentation of MEN1?
hypercalcaemia
mutation in MEN1?
autosomal dominant mutation of MEN1 tumour suppressor gene
loss of function mutation - reduced protein production
what is carney complex?
hereditary mutation of protein kinase A leading to uncontrolled cell proliferation and adrenal hyperplasia
features of carney complex?
spotty skin pigmentation
myxomas
benign or cancerous tumours
can lead to development of cushings (adrenocortical hyperplasia leads to excess cortisol production)
what is primary pigmented nodular adrenocortical hyperplasia associated with?
carney complex (causing cushings)
6 features of mccune Albright syndrome?
café au lait polyostotic fibrous dysplasia (bones) precocious puberty in females thyroid nodules GH excess cushings syndrome
what is a neuroblastoma?
tumour of primitive looking cells in the adrenal medulla which indicate differentiation towards ganglion cells
neuroblastoma is usually discovered by what age?
18 months
what cells is a phaeochromocytoma derived from and what do they do?
chromaffin cells of adrenal medulla
- chromaffin cells secrete catecholamines
features of phaeochromocytoma?
hypertension (catecholamines activate sympathetic nervous system) cardiovascular complications - heart failure - infarction - arrhythmias - stroke
how is phaeochromocytoma diagnosed?
presence of catecholamines and metabolites in the urine
CT
how is phaeochromocytoma managed?
full alpha then beta blockade
laparoscopic adrenalectomy
tumour cells in phaeochromocytoma create small nests known as what?
zellballen
which tumour is known as the 10% tumour and why?
phaeochomocytoma
10% are bilateral
10% are extra-adrenal
10% are familial (associated with MEN1 and MEN2)
phaeochromocytoma is likely to metastasise where?
bone
also lymph nodes, lung and liver
