Endocrine - 128 Flashcards
Where is CRH released from? In response to what?
Released from the hypothalamus in response to stress
What is Cushing’s Syndrome?
Excess levels of cortisol of any aetiology
What does CRH control the release of?
ACTH from the anterior pituitary
What is ACTH responsible for?
The release of glucocorticoids and other steroids from the adrenal cortex
What do high cortisol levels exert negative feedback on? What does this do?
The pituitary gland. This decreases the amount of ACTH it releases
What affect do adrenal tumours have on cortisol?
They directly release it
What affect do pituitary tumours have on cortisol?
They act to increase cortisol release from the adrenal gland
What is the most common cause of Cushing’s Syndrome?
Exogenous administration of glucocorticoids - this could be due to diseases such as asthma or rheumatoid arthritis
What is the function of calcitonin?
Decreases blood calcium levels and blood phosphate levels by helping them get deposited in bone and by stimulating excretion by the kidneys.
Calcitonin is controlled by blood calcium levels and digestive chemicals
What are the differences between T3 and T4 and what do they do?
T3 = triiodotyronine. T4 = thyroxine.
T3 is more effective but T4 is more adundant.
They regulate metabolism (breakdown of carbs, fats and synthesise proteins). They can only be made by follicular cells when iodides are available.
How do T3 and T4 get into the blood?
They are carried by thyroxine binding globin (TBG)
What is the function of PTH? How does it work?
Increases blood calcium levels and decreases blood phosphate levels.
It causes Ca and PO4 to be released from bone into the blood by increasing osteoclast activity. PTH causes the kidneys to remove PO4 ions from the urine. PTH also increases vitamin D production so that more Ca is absorbed during digestion.
How is PTH regulated?
By blood calcium levels
What cell types does the endocrine portion of the pancreas contain?
Alpha cells - secrete glucagon
Beta cells - secrete insulin
Delta cells - secrete somatostatin
What is the role of glucagon?
Works on the liver to cause the production of glucose. It is regulated by blood glucose levels directly and is secreted when levels drop, e.g. before a meal.
Glucagon prevents hypoglycaemia
What is the role of insulin?
Works on the liver to remove glucose from the blood. It does this by: making glycogen, preventing gluconeogenesis, increase glucose transport into cells.
It is regulated by blood glucose levels directly and prevents hyperglycaemia
What is the most common cause of hypercalcaemia?
Primary hyperparathyroidism
Malignancy
What does excess GH cause in both adults and children?
Adults - acromegaly
Children - gigantism
What is the most common cause of excess GH?
Pituitary adenoma
Name some signs/symptoms of acromegaly
Coarsening of facial features and soft tissues of hands & feet
Exaggerated growth of mandible
Hypertrophy of connective tissue of liver, kidney and heart
Lowered glucose tolerance - ~10% become diabetic
How is acromegaly diagnosed?
Oral glucose tolerance test -> acromegaly confirmed if elevated GH levels are not suppressed
Blood tests to look at serum IGF-1 -> elevated in acromegaly
MRI scan and echo would also be done
How would you treat acromegaly?
Surgery (if cause by pituitary adenoma)
Drug treatment - somatostatin analogues used, e.g. somatuline (lanreotide)
What are the most common causes of hyperthyroidism?
Most (~90%) are due to autoimmune thyrotoxicosis - Grave’s Disease ~75% of which.
What are some clinical features of hyperthyroidism?
- Weight loss (despite normal/increased appetite)
- diarrhoea
- breathlessness on exertion
- sinus tachycardia
- tremor
- muscle weakness
- fatigue
- sweating etc etc
Name the clinical features of Grave’s disease
Those of hyperthyroidism PLUS: - symmetrical goitre with bruit - chemosis - eyelid retraction - excess eye watering etc
What would the thyroid function test show in a patient with hyperthyroidism?
TSH would be undetectable
What is the most common cause of hypothyroidism, both worldwide and in developed countries?
Worldwide: not enough dietary iodide
Developed countries: Hashimoto’s thyroiditis
Name some symptoms of hypothyroidism
Tiredness, weight gain etc
How would you diagnose and treat hypothyroidism?
Primary hypothyroidism - increased TSH concentration
Secondary hypothyroidism - decreased free T4 & decreased TSH
Treatment = levothyroxine
Where is the problem in primary adrenal failure?
The adrenal gland. It causes adrenocorticol insufficiency
What is Addison’s disease?
Adrenal hypofunction - caused by the destruction of adrenal tissue. Usually autoimmune in origin.
In the developing world what is the main cause of Addison’s?
Tb
How might Addison’s disease first present? How would this be diagnosed?
Addisonian crisis. Measuring paired cortisol and ACTH. Presence of adrenal antibodies is helpful. Patients will have: hyperkalaemia, hyponatraemia, hypoglycaemia, increased urine Na.
How would you treat Addison’s?
IV fluids, hydrocortisone (initially) thereafter maintain patient on oral glucocorticoids
What is the difference between Cushing’s syndrome and Cushing’s disease?
Syndrome: describes signs/symptoms associated with high cortisol levels
Disease: pituitary-dependent cause, e.g. adenoma. Very rare
What is the difference between primary and secondary hypogonadism?
Primary: within the testes. Decreased testosterone, increased FSH/LH. MORE COMMON
Secondary: problem elsewhere. Decreased testosterone, decreased FSH/LH
Give an example of a primary and secondary cause of hypogonadism
1 - Klinefelters: 2 or more X chromosomes.
2 - Kallmann’s
How would you treat androgen deficiency?
Testosterone therapy, gonadotrophin therapy
In 80-90% of cases of male infertility what is the cause?
Impaired sperm production - either oligospermia or azoospermia. Could also be due to varicocoele.
How could you treat male infertility?
Intracytoplasmic sperm injection
How would a baby with foetal androgen deficiency present?
Phenotypically female at birth, blind vagina, small clitoris, testes present, bilateral inguinal hernia.
What hormones regulate Ca homeostasis?
PTH, calcitonin, Vitamin D metabolites
What is Conn’s syndrome?
Endocrine hypertension caused by excess secretion of aldosterone from the adrenal gland. Causes can include adenoma.
Treated with a low Na diet and spironalactone
43 year old lady presents with: 12 months weight gain, leg oedema, oligomenorrhoea, poor sleeping pattern.
O/E she is: Centrally plethoric, BP 180/110 mmHg.
Serum K is slightly low, 9 am cortisol = 250 nmol/l (
Cushing’s syndrome
What test results would you see for a patient with Cushing’s?
Dexamethasone is given. In a patient with Cushing’s this fails to suppress cortisol.
What test do you do to diagnose Addison’s?
Give them ACTH -> if they are normal this will spark the production of cortisol. If they have Addison’s, no cortisol is produced as the kidneys are in crisis.
Patients have hyperkalaemia with low sodium, low glucose
