Endocrinology Flashcards
Examples of water-soluble hormones
Peptides
Monoamines
Examples of fat-soluble hormones
Thyroid hormone
Steroids
Are steroid hormones stored
No they are synthesised on demand
Are water soluble hormones stored
Yes, in vesicles
Another name for adrenaline
Epinephrine
What percentage of thyroid hormones are protein bound
99% as they are not water soluble
What percentage of T3 in the circulation is secreted directly by thyroid
20%
What are the 4 hormone classes
Peptides
Amines
Iodothyronines
Cholesterol derivatives and steroids
What does vitamin D stimulate
mRNA production
What does conjugation of iodothyrosines give rise to
T3 and T4 which are stored in colloid bound to thyroglobulin
What is synergism
Combined effects of two hormones amplified e.g. glucagon with epinephrine
What is antagonism
One hormone opposes the other hormone e.g. glucagon antagonises insulin
Function of leptin
Switches off appetite and is immunostimulatory
When do leptin blood levels increase
After a meal
When do leptin blood levels decrease
After fasting
Function of Peptide YY
Inhibits gastric motility
Reduces appetite
What secretes Peptide YY
Neuroendocrine cells in ileum, pancreas and colon
Functions of cholecystokinin
delays gastric emptying
gall bladder contraction
insulin release
Satiety(via vagus nerve)
Function of Ghrelin
Growth hormone release
Increases appetite(orexigenic)
What does orexigenic mean
Stimulates appetite
What are incretins
A group of metabolic hormones that stimulate a decrease in blood glucose levels
What do alpha cells secrete
Glucagon
What do beta cells secrete
Insulin
Insulin effect on glucagon
Inhibits it
Does insulin inhibit glucagon in diabetes
No this effect is lost
Main characteristic of diabetes mellitus
Hyperglycaemia
What random plasma glucose shows diabetes
> 11 mmol/l
What fasting plasma glucose shows diabetes
> 7 mmol/l
What HbA1c value shows diabetes
> 48mmol/mol
What is type 1 diabetes
An insulin deficiency characterised by loss of beta cells due to autoimmune destruction
What is a catabolic state
when you are breaking down or losing overall mass, both fat and muscle
What is an anabolic state
Where the body builds and repairs muscle tissue
What is polydipsia
The feeling of extreme thirstiness
What is polyuria
A condition where the body urinates more than usual and passes excessive or abnormally large amounts of urine each time you urinate
What causes ketoacidosis
Breakdown/metabolism of fats in the body into ketones
What is a hyperosmolar hyperglycaemic state
A metabolic complication of diabetes mellitus characterized by severe hyperglycemia, extreme dehydration
What is severe hypoglycaemia
When you are hypoglycaemic and are unable to treat yourself ie need third party help
Two ways to treat hypoglycaemia
Insulin
Sulphonylureas
Macrovasular comlications of type 2 diabetes
Atherosclerotic cardiovascular disease
Stroke
Myocardial infarction
Peripheral arterial disease
Microvascular complications of type 2 diabetes
Diabetic kidney disease
Chronic kidney disease
Retinopathy
Peripheral neuropathy
Autonomic neuropathy
Foot problems
Diabetic ketoacidosis
What type of feedback is calcium homeostasis
Negative feedback
Parathyroid hormone actions
Decreased phosphate reabsorption
Decreased serum phosphate
Decreased FGF-23
Increased 1,25-D
Parathyroid hormone response to decreased serum calcium
Increased Calcium ion reabsorption
Bone resorption
Do small changes in serum calcium result in a big or small change in PTH
Big
Consequences of hypocalcaemia
Paraesthesia
Muscle spasm
Seizures
Basal ganglia calcification
Cataracts
ECG abnormalities
What is paraesthesia
An abnormal sensation typically tingling or prickling
What is Pseudohypoparathyroidism
Resistance to parathyroid hormone
Pituitary thyroid axis
Hypothalamus> releases TRH
TRH stimulates Pituitary to release TSH
TSH stimulates Thyroid to produce T4 and T3
GH/IGF-I axis
Hypothalamus secretes GHRH (+) and SMS (-)
These stimulate the pituitary which releases GH
GH acts on the liver
Liver produces IGF-I which has a negative effect on the hypothalamus
3 vital points of what tumours cause
Pressure on local structure e.g bitemporal hemianopia
Pressure on normal pituitary e.g hypopituitarism
Functioning tumour
What is a functioning tumour
A tumour that is found in endocrine tissue and makes hormones
Examples of functioning tumours
Prolactinoma
Acromegaly
Cushing’s disease
What is a prolactinoma
A noncancerous (benign) pituitary tumour that produces a hormone called prolactin
Who are prolactinomas more common in
Women
Effects of prolactinomas
Loss of libido
Visual field defect
Treatment of prolactinomas
Dopamine agonist eg
Cabergoline or bromocriptine
What is Goitre
Englargement of thyroid gland
What is toxic goitre
Extra thyroid gland is produced
3 mechanisms for increased thyroid hormone
Overproduction of thyroid hormone
Leakage of preformed hormone from thyroid
Ingestion of excess thyroid hormone
Most common cause of hyperthyroidism
Graves’ disease
Antithyroid drug
Thionamides
Function of thionamides
Decreases synthesis of new thyroid hormone
What is hypothyroidism
Absence / dysfunction thyroid gland
Most common cause of hypothyroidism
Hashimoto’s thyroiditis
Causes of hypothyroidism in children
Resistance to thyroid hormone
Isolated TSH deficiency
What is the normal osmolality in the body
282 - 295 mOsmol/kg
What does a lack of vasopressin cause
Cranial diabetes insipidus
What does vasopressin resistance cause
Nephrogenic diabetes insipidus
What does too much vasopressin release when it should not be released cause (syndrome of anti-diuretic hormone secretion – SIAD)
Hyponatraemia
What happens in diabetes insipidus
Your blood glucose levels are normal, but your kidneys can’t properly concentrate urine.
3 main G protein coupled receptors in water maintenance
V1a - vasculature
V2 - renal collecting tubules - reabsorption of water
V1b - pituitary
Definition of hyponatraemia
serum sodium < 135 mmol/l
Severe hyponatraemia
serum sodium < 125 mmol/l
Normal serum sodium
135-144mmol
What does reduced insulin lead to
Fat breakdown and formation of glycerol and free fatty acids
What do fatty acids do to glucose uptake
They impair it
What are free fatty acids oxidised to
Ketone bodies
What do ketones(weak organic acids) cause
Anorexia
Vomiting
What defines diabetic ketoacidosis
Hyperglycaemia (plasma glucose usually <50 mmol/l)
Raised plasma ketones (urine ketones > 2+)
Metabolic acidosis – plasma bicarbonate < 15 mmol/l
Causes of Diabetic ketoacidosis
Treatment errors e.g. insulin dose reduced or stopped
Previously undiagnosed diabetes
Management of diabetic ketoacidosis
Rehydration
Insulin
Replacement of electrolytes(K+)
treat underlying cause
Treatment must be started without delay
Treatment of type 1 diabetes
Insulin treatment
Judge carbohydrate intake
Awareness of blood glucose lowering effect of exercise
Function of type 1 diabetes management
To restore the physiology of the beta cell
Factors that make it difficult for people with diabetes to sustain effective self management
Risk of hypoglycaemia
Too arduous a treatment
Risk of weight gain
Interference with lifestyle
Lack of sufficient training from diabetes teams
What is the commonest type of monogenic diabetes
Maturity-onset diabetes of the young (MODY)
Is MODY autosomal dominant
Yes
Is MODY Non-insulin dependent
Yes
What is the glucose sensor of beta cells
GCK(Glucokinase gene)
How does acromegaly cause diabetes
Excessive secretion of growth hormone causes insulin resistance to rise
How does Pheochromocytoma cause diabetes
Increased Gluconeogenesis
Decreased glucose uptake
What drugs increase insulin resistance
Glucocorticoids
What drugs increase insulin resistance
Glucocorticoids
Common signs of adrenal insufficiency
Hypotension and cardiovascular collapse
Fatigue
Fever
Hypoglycaemia
Hyponatraemia and hyperkalaemia
Pharmaceutical name for cortisol
Hydrocortisone
What are circadian rhythms
Physical, mental and behavioural changes that follow a daily cycle
Example of primary adrenal insufficiency
Addison’s disease
Example of secondary adrenal insufficiency
Hypopituitarism
Example of tertiary adrenal insufficiency
Suppression of HPA
Is it the adrenal medulla or cortex that is controlled by the pituitary gland
The adrenal cortex
Where is growth hormones main site of action to stimulate IGF1 release
Liver
Typical features of cortisol deficiency
Hypotension
Muscle aches
Weight loss
Lethargy
