Endo Flashcards
What hormones are released via circadian rhythm?
ACTH, TSH, GH, cortisol, prolactin
Summarise T3 and T4 production and release
- iodide actively transported into follicular cells. Travel to the colloid cells
- Oxidised to iodine
- Binds to tyrosine residues on the thyroglobulin molecule, under the action of thyroid peroxidase
- Binds to one iodine (T1) or two (T2)
- When thyroid stimulated, T1 and T2 are cleaved from tyrosine, still attached to thyroglobulin
- Join together to form T3 and T4
- TSH stimulates movement of T3/T4 to go to secretory cells
What connects the pituitary gland to the hypothalamus? What does it also contain?
Infundibulum. Also contains axons from neurones in the hypothalamus
What is the difference between the anterior and posterior pituitary gland?
- anterior: The release of hormones is under the control of the hypothalamus, which communicates with the gland via neurotransmitters secreted into the hypophyseal portal vessels. These vessels ensure that the hypothalamic hormones remain concentrated, rather than being diluted in the systemic circulation.
- posterior: hormones produced in the hypothalamus, stored in the posterior pituitary (extension of the hypothalamus).
What are the hormones of the anterior pituitary? And what hormones stimulate them from the hypothalamus
- CRH –> ACTH
- GHRH –> GH
- GnRH –> LH and FSH
- TRH –> TSH
- Dopamine inhibits prolactin
What is the action of FSH and LH?
Gonadotrophs. Stimulate germ cell development.
What is the action of GH?
Somatotroph. Stimulates growth and protein synthesis. Also inhibits insulin. Acts on liver to increase protein synthesis and stimulate IGF-1. Acts on skeleton to increase cartilage proliferation
What is the action of ACTH?
Stimulates cortisol release from zona fasiculata. Also; androgens from zona reticularis and adrenaline from the medulla. Regulates and breaks down proteins, fats, carbohydrates. Anti-inflammatory, suppressed in immune response
What is the action of TSH?
release of T3 and T4. Rate of metabolism, increase protein synthesis, increase breathing rate + heart rate + cardiac output. Growth rate acceleration
What is the action of prolactin?
milk production
What hormones are stored in the posterior pituitary?
ADH and oxytocin
What is the action of ADH?
retain volume, vasoconstriction, increased blood pressure. Release due to stress, trauma, blood loss, decreased BP, increased blood CO2
What is the action of oxytocin?
Uterine muscle contraction
What is the most common anterior pituitary tumour?
benign pituitary adenoma
What is Sheehan’s?
Pituitary infarction after labour
What are the three presentation points of anterior pituitary tumours?
- pressure on local structures (hydrocephalus, bitemporal hemianopia)
- pressure on normal pituitary: hypopituitarism
- functional tumour: hyperpituitarism
What are three examples of functional tumours?
- prolactinoma: increased prolactin. Treated with dopamine agonist (eg, cabergoline). Commonest in young women
- acromegaly: increased GH
- Cushings: increased CTH and cortisol
What should glucose levels be between?
3.5 and 8.0 mmol/L
What is insulin? where is it produced? What is its actions?
- produced in the beta cellas of islets of langerhanns
- biphasic release
- pro-insulin = precursor. When it’s cleaved, leaves c protein
- suppresses hepatic glucose output: decreases glycogenolysis and gluconeogenesis. Increases glucose uptake. Suppresses lipolysis and muscle breakdown
What hormones (other than insulin and glucagon) control glucose?
adrenaline, GH and cortisol
What is the definition of diabetes mellitus?
syndrome of chronic hyperglycaemia, due to relative insulin deficiency, resistance or both
What is type 1 DM?
disease of insulin deficiency, usually due to autoimmune destruction of the beta cells of the pancreas
Why does DKA occur in T1DM? what is the definition of DKA?
reduced muscle uptake of glucose and increased beta fatty acid oxidation, leads to increased acetyl CoA, increased ketone bodies. Acidosis
- DKA: inability of haemoglobin to bind to O2 due to acidity
When is diabetes a secondary disease?
pancreatic pathology: eg, endocrine disease (acromgealy, Cushings)
What is type 2 DM?
disease of combination of insulin resistance and less severe insulin deficiency. Insulin develops post receptor (GLUT-4: peripheral receptor, GLUT-2 in pancreas)
Why might T2DM have amyloid deposits in islets?
Due to amyloid being co-secreted with insulin
Why does DKA not occur in T2DM?
There is normally still some presence of insulin
What is the triad of presentation of DM?
polydipsia, polyuria, weight loss. More marked in type 1
What complaints may be a presentation of DM?
- staph skin infection
- retinopathy
- polyneuropathy
- erectile dysfunction
When might acathrosis nigracans be seen?
T2DM. Black skin pigmentation
How is diabetes diagnosed?
- random and fasting plasma glucose.
- random: >11.1mmol/L
- fasting >7mmol/L
What are the symptoms of DKA?
dehydration, breath smelling of pear drops, Kaussmaul’s respiration, drowsiness, vomiting, low temperature, coma
What are the risk factors of DKA?
- stopping insulin
- surgery
- MI
- infection
- pancreatitis
- undiagnosed diabetes
What is the treatment for type 1 diabetes
diet and insulin
What is the tx for T2DM?
Diet and exercise change. Blood pressure and hyperlipidemia control.
- biguanide (oral metformin): reduces rate of liver gluconeogenesis, increases insulin sensitivity
- sulfonylurea (eg, oral gliazide): promotes insulin release
- insulin
- sulfonylurea receptor binders
- GLP
What is the presentation of hyperosmolar hyperglycaemia state?
severe dehydration, decreased consciousness, hyperglycaemia, hyperosmolarity, no ketones in blood/urine
why is heparin given after a hyperosmolar hyperglycemia state?
Because it predisposes to MI, stroke, arterial insufficiency to lower limbs
What are possible complications of diabetes?
- retinopathy: danger to retina, glomerulus, nerve sheath
- nephropathy: thickening of basement membrane due to hyperglycaemia. Can lead to nephrotic syndrome
- neuropathy: pain, autonomic features (eg, diarrhoea, constipation, ED), insensitivity, eye palsies
- diabetic foot ulceration
- peripheral vascular disease (due to diabetes being a risk factor for atherosclerosis)
- infections: poor glycaemic control affects WBC. Susceptible to staph skin infections, UTI
What is the glucose level for hypoglycaemia?
<3 mmol/L
What is Graves disease?
autoimmune hyperthyroidism.
What is a typical presentation of Graves?
tachycardia, tremor, goitre, graves ophthalmology (eyes bulging and lid retraction), graves dermopathy, decreased weight
What is dx for Graves?
- presence of TSHR-Ab, low TSH, high T3 and T4
What is the treatment for Graves?
- ophthamology: IV methylprednisolone
- beta blockers for symptoms
- carbemazole stops T4 to T3
- PTU: also antithyroid drug
- radioactive iodine control (local tissue damage)
- subtotal or total thyroidectomy
What is a common side effect of carbemazole?
Sore throat
What is De Quervains thyroiditis?
viral infection induced hyperthyroidism. usually accompanied with fever, etc.
What is Hashimoto’s thyroiditis?
autoimmune hypothyroidism. Aggressive destruction of thyroid cells, with some regeneration (goitre).
what is the dx for Hashimoto’s thyroiditis?
High TSH, low T3 and T4. TPO-Ab present
What is the tx for Hashimoto’s thyroiditis?
- thyroxine
- resection of obstructive goitre
What is a potential compx of Hashimoto’s thyroiditis and why?
Hyperlipidaemia, as T3/T4 needed to break down carbohydrates
What are the four types of thyroid carcinoma? Which is the most common? What is the prognosis of each?
- papillary: most common. Good prognosis
- follicular. Good prognosis
- anaplastic. Poor prognosis
- medullary
What is the dx of thyroid carcinoma?
- fine needle aspiration biopsy
What is the treatment of thyroid carcinoma?
- radioative I131
- levothyroxine to suppress TSH (growth factor for the cancer)
- chemotherapy
- thyroidectomy
What is Cushing’s
- hypercortolism
- excess glucocorticoids
- usually due to a pituitary tumour causing ACTH.
what is the most common cause of cushings?
bilateral adrenal hyperplasia, from ACTH secreting adenoma
What is the symptoms of Cushings?
obese (buffalo hump), moon face, purple bruising, purple striae, hypertension, mood change, increased infections
What is the dx for Cushings?
- random plasma test for cortisol
- 48 hour low dose dexamethasone (should trigger negative feedback). No suppression in Cushings disease
- urinary free cortisol
- plasma ACTH: undetectable = tumour
detectable= free source (eg, ectopic) - CRH test
What is the tx for Cushings?
- stop steroids
- surgical removal of tumour
- cortisol synthesis inhibition: metyrapone
What is released from the zona reticularis?
Androgens
What is released from zona fasciculata?
cortisol
What is acromegaly?
Increased GH, and thus IGF-1 (this is how GH exerts its effects). Due to a benign GH producing adenoma
What are comorbidties of acromegaly?
impaired glucose tolerance, DM, sleep apnoea, HTN, heart failure, arthritis
What is the dx for acromegaly?
- glucose tolerance test. should reduce GH
- serum IGF-1 and GH
- MRI
What is the tx for acromegaly?
- trans-sphenoidal surgery
- somatostain analogue to inhibit GH release
- GH receptor antagonists: suppress IGF-1. Eg, pegvisomant
- dopamine agonist: cabergoline
What are the symptoms for prolactinoma?
amennorhoea, infertility, galactorhoea, low libido, local compressive effects
Whatis the tx for prolactinoma?
dopamine agonist: cabergoline