Endocrine Flashcards
Give 2 examples of water-soluble hormones
- Peptides
2. Monoamines
Give 2 examples of fat-soluble hormones
- Thyroid hormone
2. Steroids
How are peptide hormones released?
In pulses or bursts
How are peptide hormones synthesised?
Preprohormone > prohormone > hormone
How is adrenaline synthesised?
Phenylalanine > tyrosine > L-DOPA > DA > NA > Adr
What is NA converted to?
Normetanephrine
What is Adrenaline converted to?
Metanephrine
How does adrenaline cause vasoconstriction?
Binds alpha adrenoceptor to stimulate secondary messenger system and Ca is released to exert tissue function
How does adrenaline cause bronchodilation?
Binds beta adrenoceptor > cAMP converts inactive protein kinase to active protein kinase
What thyroid hormone is most abundant?
T4
What thyroid hormone is more active?
T3
What gives rise to T3 and T4?
Iodine incorporates tyrosine molecules to form iodothyrosines which conjugate to form T3/T4
What stimulates T3/T4 synthesis?
TSH
What can control hormone secretion?
- Basal secretion
- Superadded rhythms
- Release inhibiting factors
- Releasing factors
What can control hormone action?
- Hormone metabolism
- Hormone receptor induction
- Hormone receptor downregulation
- Synergism
- Antagonism
What is synergism?
Combined effects of 2 hormones amplified
Pituitary gland growth can press on which cranial nerves?
CN III, IV, VI, V
What controls vasopressin?
- Blood volume
2. Osmolality
How can the pituitary dysfunction?
- Tumour mass effects
- Hormone excess
- Hormone deficiency
Give 5 functions of thyroid hormone
- Accelerates food metabolism
- Increases protein synthesis
- Increases ventilation rate
- Increases HR and CO
- Accelerates growth rate
What % of the UK population are obese?
22%
Why are shift workers more at risk of obesity?
Their cortisol rhythms shift to being highest when sleeping instead of when waking
What does weight regulation depend on?
Environment and genes
What influences the satiety cascade?
- Meal quality
- Meal quantity
- Nutrient status
- Energy balance
Where is the hunger centre?
Lateral hypothalamus
Where is the satiety centre?
Ventromedial hypothalamic nucleus
Name 3 hormones heavily involved in appetite regulation
- Leptin
- Insulin
- Ghrelin
Where is leptin expressed?
White fat
What is the function of leptin?
Switches off appetite and is immunostimulatory
When do leptin levels increase?
After a meal
What happens in an individual with increased fat regarding leptin?
Leptin expression increases > more leptin in hypothalamus > POMC activation > no appetite suppression
Where is peptide YY secreted?
Neuroendocrine cells in ileum, pancreas and colon
What is the function of peptide YY?
Inhibits gastric motility and reduces appetite
What is the function of cholecystokinin?
- Delays gastric emptying
- Gall bladder contraction
- Insulin release
- Satiety
What is the function of ghrelin?
- Growth hormone release
2. Appetite
When are ghrelin levels high?
When fasting
What is POMC?
Proopiomelanocortin
What do POMC produce when bound?
Cortisol
What happens in POMC deficiency?
- ACTH deficiency
- Pale skin
- Adrenal insufficiency
- Hyperphagia
- Obesity
What are the effects of increased PTH?
- Increase bone resorption
- Increase Ca absorption in gut
- Increase Ca reabsorption in kidney
Why might changes in PTH be appropriate?
To maintain Ca balance
Give 4 symptoms of hypocalcaemia
- Paraesthesia
- Muscle spasm
- Seizure
- Cataracts
Give 3 signs of hypocalcaemia
- Long QT interval
- Chvostek’s sign
- Trousseau’s sign
What can cause hypocalcaemia?
Undermineralised bones and pseudofractures
Give 3 syndromes relates to hypoparathyroidism
- Di George
- Kenney-Caffey
- Sanjad-Sakati
Give 3 symptoms of Di George syndrome
- Hypoparathyroidism
- Cleft palate
- Thymic aplasia
What causes Di George syndrome?
Developmental abnormality of 3rd and 4th branchial pouches
What causes functional hypoparathyroidism?
Magnesium deficiency
Give 4 symptoms of pseudohypoparathyroidism
- Short stature
- Obesity
- Round facies
- Short 4th metacarpals
What causes pseudohypoparathyroidism?
PTH resistance
Give 4 symptoms of pseudopseudohypoparathyroidism
- Short stature
- Normal Ca metabolism
- Round facies
- Obesity
Give 4 symptoms of hypercalcaemia
- Thirst
- Nausea
- Constipation
- Confusion
Give 3 causes of hypercalcaemia
- Malignancy
- Primary hyperparathyroidism
- Thiazides
Why is hypercalcaemia seen in malignancy?
- Serum Ca rises
- PTH decreases
- Reduced bone resorption, Ca absorption and Ca reabsorption
Give 4 consequences of primary hyperparathyroidism
- Bones - osteoporosis
- Kidney Stones
- Psychic Groans - confusion
- Abdominal Moans - constipation
What causes most primary hyperparathyroidism?
Single benign adenoma of one of 4 thyroid glands
What are the consequences of tertiary hyperparathyroidism?
- Nodular hyperplasia
- Autonomy
- Hypercalcaemia
What causes tertiary hyperparathyroidism?
Renal failure so can’t activate vitamin D
What is seen in secondary hyperparathyroidism?
Excessive secretion of PTH in response to hypocalcaemia
Give 3 symptoms of secondary hyperparathyroidism
- Osteoporosis
- Kidney stones
- Polyuria
How are primary and secondary hyperparathyroidism treated?
Diet based
How is tertiary hyperparathyroidism treated?
Cinacalcet and surgery
Where does glucose come from?
Liver
How is glucose made?
- Breakdown of glycogen
2. Gluconeogenesis
Where does ingested glucose go?
40% to liver, 60% to periphery
Where are insulin and glucagon secreted?
- Endocrine pancreas
2. Islet of Langerhans
What cells secrete insulin?
Beta cells
What cells secrete glucagon?
Alpha cells
How is insulin secreted?
- Glucose enters and is metabolised
- ADP and ATP made
- K channels close
- Depolarisation of membrane
- Ca inwardly enters cell
- Insulin secretory granules stimulated
- Insulin released
What is mobilised to the cell surface to allow glucose entry to cells?
GLUT4
What is the function of insulin?
- Reduces glycogenolysis
- Reduces gluconeogenesis
- Increases glucose uptake into cells
- Suppresses lipolysis
- Suppresses muscle breakdown
What are the functions of glucagon?
- Increases glycogenolysis
- Increases gluconeogenesis
- Reduce glucose uptake
- Stimulate lipolysis
- Stimulate muscle breakdown
What is diabetes mellitus?
A disorder of carbohydrate metabolism characterised by hyperglycaemia
How does diabetes cause morbidity?
- Acute hyperglycaemia
- Diabetic ketoacidosis
- Chronic hyperglycaemia
- Hypoglycaemia
Give 3 serious complications of diabetes
- Diabetic retinopathy
- Renal disease
- Stroke
What FBG is seen in diabetes?
> 7 mmol/L
What HbA1c is seen in diabetes?
48 mmol/mol (6.5%)
What is the pathogenesis of diabetes?
Loss of beta cells due to autoimmune destruction called insulitis
What are the stages of diabetes?
- Genetic predisposition
- Insulitis beta cell injury
- Pre-diabetes
- Diabetes
What proportion of beta cells remain when a DM diagnosis is made?
10%
What is the result of insulin secretion failure?
- Continued glycogenolysis
- Unrestrained lipolysis and muscle breakdown
- Increase in hepatic glucose output
What are the results of untreated DM?
- Increase circulating glucagon
- Increased cortisol and Adrenaline
- Weight loss
What is the result of reduced insulin?
- Lipolysis
2. Formation of glycerol and FFA
What is the function of FFA?
They are oxidised to form ketone bodies
What causes ketoacidosis?
Absence of insulin and rising counterregulatory hormones leads to increasing hyperglycaemia and rising ketones
What are the signs and symptoms of ketoacidosis?
- Anorexia
- Vomiting
- Dehydration
- Hyperglycaemia
- Circulatory collapse
What causes T2DM?
Impaired insulin secretion and insulin resistance resulting in impaired glucose tolerance
What is the pathogenesis of T1DM?
Severe insulin deficiency due to autoimmune destruction of the beta cell
What is the pathogenesis of T2DM?
Insulin resistance and impaired insulin secretion due to a combination of genetic predisposition and environmental factors
Why would T2DM patients end up on insulin?
Lipotoxicity
Which insulin mimics normal physiology?
Basal bolus insulin
What is the problem with basal analogue insulin?
There is a lag before it reaches hepatic portal system – takes a while for insulin to kick in so sugars rise from a meal when this is happening
What insulin approaches are there for T2DM?
- Once daily basal insulin
- Twice daily basal insulin
- Basal bolus therapy
Give 2 advantages of basal insulin in T2DM
- Simple for patient, self-administered
2. Less risk of hypoglycaemia at night
Give 1 disadvantage of basal insulin in T2DM
Doesn’t cover meals
What is the best T1DM treatment?
Basal bolus insulin therapy
What is the BGL for hypoglycaemia?
3.9 mmol/L
What is hypoglycaemia?
Low plasma glucose causing impaired brain function neuroglycopenia
Give 5 symptoms of hypoglycaemia
- Trembling
- Palpitations
- Confusion
- Weakness
- Nausea
What are the symptoms of severe hypoglycaemia?
- Reduced conscious levels
- Convulsions
- Coma
What are 3 risk factors for severe hypoglycaemia in T1DM?
- Hx of severe episodes
- Renal impairment
- Extremes of age
What are 3 risk factors for severe hypoglycaemia in T2DM?
- Age
- Cognitive impairment
- Depression
What is the aim for HbA1c in T2DM?
<7.0%
What is the treatment for hypoglycaemia?
- 15g fast-acting carbohydrate
2. Eat a long-acting carbohydrate to prevent recurrence of symptoms
What are the effects of the pituitary gonadal axis not working properly?
Men > low testosterone
Women > no periods
What is the consequence of HPA axis malfunction?
CV collapse
What inhibits prolactin secretion?
Dopamine
What is craniopharyngioma?
Condition causing a lack of pituitary function and issues with satiety and appetite regulation
What is Sheehans?
During pregnancy pituitary doubles in size and can outstrip its blood supply and infarct
What is the result of pituitary tumours?
- Pressure on local structures
- Pressure on normal pituitary
- Functioning tumour
What conditions can arise from functioning pituitary tumours?
- Prolactinoma
- Acromegaly
- Cushing’s
What can be the result of pressure on local structures from pituitary tumours?
- Bitemporal hemianopia
- Headaches
- Ptosis
What are 3 symptoms of tumours causing pressure on the pituitary?
- No body hair
- Menstrual dysfunction
- Central obesity
What is the pathogenesis of Cushing’s disease?
Chronic, excessive and inappropriate elevated levels of circulating plasma glucocorticoids
What is the presentation of Cushing’s disease?
- Central obesity
- Decreased linear growth
- Thin skin
- Muscle wasting
- Easy bruising
- Hirsutism
What are the causes of Cushing’s disease?
- Excess glucocorticoid
- Tumour producing too much ACTH
- Adrenal tumour making too much cortisol
What happens to the adrenal axis in Cushing’s disease?
Feedback isn’t working as tumour is resistant to it so continues to make ACTH
What are the symptoms in Cushing’s syndrome?
- Moon face
- Hirsutism
- Facial plethora
- Acne
- Thinned scalp hair
Give 5 clinical features of Cushing’s
- Diabetes
- Hypertension
- Immune suppression
- Depression
- Loss of libido
How is Cushing’s syndrome screened?
- High urinary free cortisol
- High serum cortisol
- High plasma night cortisol
- High late-night salivary cortisol
What imaging is used in Cushing’s disease?
Pituitary MRI
What is the treatment for Cushing’s?
- Adrenal blockade
- Surgery
- Radiotherapy
What is the pathogenesis of acromegaly?
GH hormone secreting tumour causing IGF1 production to increase in liver which gives rise to clinical features
What is the mean age of diagnosis in acromegaly?
44
Give 3 co-morbidities of acromegaly
- Arthritis
- Diabetes
- Sleep apnoea
How is acromegaly diagnosed?
- Clinical features
- GH
- IGF-1
What are 5 clinical features in acromegaly?
- Acral enlargement
- Wide jaw
- Large lips
- Excessive sweating
- Arthralgias
What is the test for acromegaly?
75mg glucose tolerance test
What is the Tx for acromegaly?
- Pituitary surgery
- Medical therapy
- Radiotherapy
What is the cure rate for micro adenoma surgery?
90%
What is the cure rate for macroadenoma surgery?
<50%
What are the disadvantages of radiotherapy in acromegaly?
- Delayed response
- Hypopituitarism
- Secondary tumours
What drugs can be used for acromegaly?
- Cabergoline (DA agonist)
- Samatostatin analogues e.g. octreotide
- GH receptor antagonist e.g. pegvisomant
What is the incidence of prolactinoma?
1 in 10,000
What causes prolactinoma?
Lactotroph cell tumour of the pituitary causing too much prolactin
What are the clinical features of prolactinoma?
- Headache
- Bitemporal hemianopia
- Menstrual irregularity
- Infertility
What can be used to treat prolactinoma?
- Cabergoline
2. Bromocriptine
When do cortisol levels peak?
Around an hour after waking
What is the cause for 60% of Addison’s disease cases?
Autoimmune adrenalitis
What is seen in congenital adrenal hyperplasia (CAH)?
Can’t produce cortisol so ACTH levels rise; high androgens but low cortisol so ambiguous genitalia and salt losing crises
How common is CAH?
1:15,000
What is secondary adrenal insufficiency?
Hypopituitarism
What is seen in secondary adrenal insufficiency?
- Apoplexy
- Hypophysitis
- Pituitary macroadenoma
What are the symptoms of adrenal insufficiency?
- Fatigue
- Weight loss
- Poor recovery from illness
- Adrenal crisis
What are the signs of adrenal insufficiency?
- Pigmentation
- Pallor
- Hypotension
What is the biochemistry in adrenal insufficiency (AI)?
- Low Na
- High K
- Eosinophilia
- High TSH
What ACTH levels of seen in Addison’s?
> 22ng/L
What ACTH levels are seen in secondary AI?
<5ng/l
What is the investigations for Addison’s disease?
- Adrenal antibodies
- Long chain FA
- Imaging