Endocrinology Flashcards
Where does ingested glucose go?
40% to liver
60% to periphery (mostly muscle)
What is glucagon?
A peptide hormone that raises the concentration of glucose and fatty acids in the bloodstream
Which cells secrete glucagon?
Alpha cells of the Islets of Langerhans (in pancreas)
Which cells secrete insulin?
Beta cells of the Islets of Langerhans (in pancreas)
What is paracrine ‘crosstalk’ between alpha and beta cells?
When beta cells secrete insulin, there is tonic inhibition on alpha cells so that they cannot release glucagon
What are examples of counterregulatory hormones?
Glucagon, adrenaline, cortisol and growth hormone
What is type 1 diabetes?
Autoimmune destruction of pancreatic beta cells leading to complete insulin deficiency
Describe the epidemiology of type 1 diabetes
- Usually presents between ages 5-15
- 10% of diabetes diagnoses
Name the 3 risk factors for type 1 diabetes
- Family history (HLA DR3-DQ2 or HLA DR4-DQ8)
- Northern European
- Other autoimmune disease
Describe the pathophysiology of type 1 diabetes
- Autoantibodies attach to beta cells
- This causes an insulin deficiency and leads to hyperglycaemia
- Insulin absence results in an increased breakdown of glycogen (hepatic gluconeogenesis)
- This decreases peripheral glucose causing glycosuria
Name 5 symptoms of type 1 diabetes
- Polydipsia
- Polyuria
- Weight loss (BMI<25)
- Fatigue
- Ketosis
What is type 2 diabetes?
Patient gradually becomes insulin resistant or pancreatic beta cells fail to secrete enough insulin. Progresses from impaired glucose tolerance
Name 6 causes of type 2 diabetes
- Reduced insulin secretion
- Increased insulin resistance
- Gestational diabetes
- Steroids
- Cushing’s
- Chronic pancreatitis
Name the 4 risk factors for type 2 diabetes
- Lifestyle (e.g. obesity, lack of exercise, excess of alcohol, diet)
- Asian men
- Age 40 and above
- Hypertension
Name 6 symptoms of type 2 diabetes
- Polydipsia
- Polyuria
- Glycosuria
- Central obesity
- Blurred vision
- Fatigue
What are the normal and diabetes levels of fasting plasma glucose?
Normal = <6mmol/L
Diabetes = >7mmol/L
* pre diabetes = between
What are the normal and diabetes levels of random plasma glucose?
Normal = <11mmol/L
Diabetes = >11mmol/L
What are the normal and diabetes levels of HbA1c?
Normal = <42mmol/L
Diabetes = >48mmol/L
* pre diabetes = between
What does HbA1c measure?
Measures the amount of glucose latched onto circulating RBCs. As RBCs live for about 3 months, it tells you about glucose levels throughout the last 3 months
What is the 1st line management for type 2 diabetes?
Lifestyle changes:
- Dietary advice
- Weight control
- Smoking cessation
- Decreased alcohol intake
- Encourage exercise
- Regular blood glucose and HbA1c monitoring
What is the 2nd line management for type 2 diabetes?
Medications:
- Biguanides
- Dual therapy (biguanides + …)
- Triple therapy
- Insulin
What are biguanides? Give an example and side effects
- E.g. metformin
- Cause decreased gluconeogenesis in the liver
- Increase cell sensitivity to insulin
- Side effects include GI disturbances
What are sulfonylureas? Give an example and side effects
- E.g. gliclazide
- Promote insulin secretion by binding to beta cells
- Side effects include hypoglycaemia and weight gain
What is diabetic ketoacidosis (DKA)?
Complete lack of insulin resulting in high ketone production (serious complication of type 1 diabetes)
Describe the pathophysiology of diabetic ketoacidosis
- Absence of insulin causes uncontrolled catabolism (unrestrained gluconeogenesis) which decreases peripheral glucose uptake –> hyperglycaemia
- Hyperglycaemia causes osmotic diuresis and dehydration
- Increase in circulating free fatty acids which are oxidised to Acetyl CoA which form ketone bodies (which are acidic –> acidosis)
Name 5 signs of diabetic ketoacidosis
- Kussmaul’s breathing (deep and laboured breathing)
- Pear drop breath
- Hypotension
- Tachycardia
- Reduced tissue turgor
Name 5 symptoms of diabetic ketoacidosis
- Extreme diabetes symptoms
- Nausea and vomiting
- Confusion and reduced mental state
- Lethargy
- Abdominal pain
What are the investigations for patients with diabetic ketoacidosis?
- Random plasma glucose >11mmol/L
- Plasma ketones >3mmol/L
- Blood pH <7.35 or bicarb <15mmol/L
- Urine dipstick = glucosuria and ketonuria
- Serum U+E = raised urea and creatine
- Serum U=E = decreased total K+ and increased serum K+
What is the treatment for diabetic ketoacidosis?
- ABC management
- Replace fluid (0.9% saline IV)
- IV insulin
- Restore electrolytes
What is hyperosmolar hyperglycaemia state (HHS)?
Marked hyperglycaemia, hyperosmolality and mild/no ketosis (serious complication of type 2 diabetes)
Describe the pathophysiology of hyperosmolar hyperglycaemia state
- Low insulin causes increased gluconeogenesis –> hyperglycaemia (however there are sufficient enough levels of insulin to inhibit ketogenesis)
- Hyperglycaemia causes osmotic diuresis and dehydration
Name 5 symptoms of hyperosmolar hyperglycaemic state
- Extreme diabetes symptoms
- Confusion and reduced mental state
- Lethargy
- Hyperosmolality
- No ketones in blood or urine
What are the investigations for patients with hyperosmolar hyperglycaemic state?
- Random plasma glucose >11mmol/L
- Urine dipstick = glycosuria
- High plasma osmolality
- U+E = decreased total K+ and increased serum K+
What is the treatment for hyperosmolar hyperglycaemia state?
- Replace fluid (0.9% saline IV)
- Insulin
- Restore electrolytes
- Low molecular weight heparin (to decrease risk of thromboembolism)
What is hypoglycaemia?
Low glucose levels
How is hypoglycaemia classified?
- Level 1 = plasma glucose <3.9mmol/L and no symptoms
- Level 2 = plasma glucose <3mmol/L
- Non-severe = patient has symptoms but can self treat and cognitive function is mildly impaired
- Severe = patient has impaired cognitive function sufficient to require external help tor recover
Name 5 autonomic symptoms of hypoglycaemia
- Trembling
- Palpitations
- Sweating
- Anxiety
- Hunger
Name 6 neuroglycopenic symptoms of hypoglycaemia
- Difficulty concentrating
- Confusion
- Weakness
- Drowsiness/dizziness
- Vision changes
- Difficulty speaking
Name 2 non specific symptoms of hypoglycaemia
- Nausea
- Headache
What is the treatment for hypoglycaemia?
- Treat with 15g fast-acting carbohydrate
- Retest in 15 mins to ensure blood glucose >4mmol/L
- Eat long-acting carbohydrate
What is hyperthyroidism and what are the two types?
Excess thyroid hormone
Primary = abnormal increased thyroid function
Secondary = abnormal increased TSH production
Name 5 primary causes of hyperthyroidism
- Grave’s disease
- Nodules (multinodular goitre, toxic adenomas)
- Iodine excess
- Amiodarone
- Metastatic follicular thyroid cancer
Name a secondary cause of hyperthyroidism
TSH pituitary tumour
What is Grave’s disease?
An autoimmune condition in which there is increased production of T3 and T4 due to antibodies binding to TSH receptors
Describe how Grave’s disease works
- IgG autoantibodies (anti-TSHR-Ab) are produced which bind to and activate thyrotropin receptors
- This results in the increased production of thyroid hormones (T3 and T4)
What does Grave’s disease cause?
- Symptoms of hyperthyroidism
- Thyroid eye disease = eyelid retraction, periorbital swelling, proptosis/exophthalmos
- Pretibial myxoedema
- Thyroid acropachy
What is pretibial myxoedema?
Accumulation of excess glycosaminoglycans in the dermis and subcutis of the skin
What does thyroid acropachy cause?
- Nail clubbing
- Painful swelling of digits/toes
- Periosteal reaction (bone growth)
What are the 5 risk factors for hyperthyroidism?
- Being female (F:M = 9:1)
- Smoking
- Stress
- Genetic (HLA-DR3)
- Other autoimmune diseases
Describe the pathophysiology of hyperthyroidism
- Increased T3 causes an increase in metabolic rate
- This activates the sympathetic nervous system and so increases cardiac output, bone resorption etc.
What are the 3 signs of hyperthyroidism?
- Periorbital swelling
- Goitre
- Tachycardia
What are the 8 symptoms of hyperthyroidism?
- Hot and sweaty
- Diarrhoea
- Weight loss
- Anxiety/restlessness
- Hyperphagia (increased desire to eat)
- Oligomenorrhoea (irregular menstrual bleeding)
- Palpitations
- Tremor
What are the investigations for patients with hyperthyroidism?
- Thyroid function tests (TFTs) = high T3/T4 but low TSH (primary), high T3/T4 and high TSH (secondary)
- Thyroid autoantibodies (anti-TSHR)
- US and CT head
What is the treatment for hyperthyroidism?
- Drug management
- Radioiodine
- Thyroidectomy
Describe drug management for hyperthyroidism
1st line = carbimazole (blocks synthesis of T4)
2nd line = propylthiouracil (prevents conversion of T4 into T3)
Beta blockers = provide rapid symptom relief
What is hypothyroidism and what are the two types?
Lack of thyroid hormone
Primary = abnormal decreases thyroid function
Secondary = abnormal decreased TSH production
Name 5 primary causes of hypothyroidism
- Hashimoto’s
- Primary atrophic hypothyroidism
- Iodine deficiency
- Drugs
- Post thyroidectomy/radioiodine
Name a secondary cause of hypothyroidism
Hypopituitarism
What is Hashimoto’s?
An autoimmune condition in which antibodies attack the thyroid causing inflammation and dysfunction, lowering T3/T4 levels
What are the 3 risk factors for hypothyroidism?
- Being female (F:M = 6:1)
- Post partum
- Other autoimmune diseases
Describe the pathophysiology of hypothyroidism
- Decreased T3 levels mean that there is an insufficient amount for normal body functions
What are the 3 signs of hypothyroidism?
- Delayed reflexes
- Goitre
- Bradycardia
What are the 8 symptoms of hypothyroidism?
- Cold intolerance
- Constipation
- Weight gain
- Fatigue and lethargy
- Loss of appetite
- Menorrhagia (heavy menstrual bleeding)
- Brain fog
- Depression
What are the investigations for patients with hypothyroidism?
- Thyroid function tests (TFTs) = low T3/T4 but high TSH (primary), low T3/T4 and low TSH (secondary)
- Autoantibodies (anti-TPO)
What is the treatment for hypothyroidism?
Levothyroxine (T4)
What are 4 other causes of thyroid disorders?
- De Quervain’s Thyroiditis
- Post-partum thyroiditis
- Amiodarone
- Lithium toxicity
What is De Quervain’s Thyroiditis?
- Mild hyperthyroidism following a viral infection of the thyroid
- Lasts for a few weeks
- Pain and tenderness over thyroid gland
- Flu-like symptoms
- Beta blockers given to relief symptoms, no other treatment given
What is post-partum thyroiditis?
- Mild hyperthyroidism which develops in the first year after childbrith
- Lasts for a few weeks
- Often very few symptoms
- Beta blockers given to relief symptoms, no other treatment given
What is amiodarone and how does it affect the thyroid?
- An iodine-containing drug used for the treatment of certain irregularities of heart rhythm
- Can cause hyperthyroidism or hypothyroidism
- Blood thyroid levels should be checked before and throughout taking the drug
What is lithium toxicity and how does it affect the thyroid?
- Lithium carbonate is used for depression and mania
- It can cause goitres and hypothyroidism
- Thyroxine is given alongside treatment
What are the two main types of thyroid cancer?
- Papillary cancer - tumour contains papillae or fronds
- Follicular cancer - distinctly abnormal appearance with some structures that resemble the normal follicles of the thyroid
How is thyroid cancer diagnosed?
Fine needle aspiration (type of biopsy) or following surgery
How is papillary cancer treated?
Total thyroidectomy as there is a tendency for the cancer to occur in various places throughout the gland
How is follicular cancer treated?
Hemithyroidectomy as it tends to only occur in one part of the thyroid
What additional treatment is given following thyroidectomys?
- Radioactive iodine given to remove any remaining cancer cells
- Thyroxine (T4) given to reduce TSH levels in the blood
Where is the pituitary gland?
Embedded in the sella turcica just below the optic chiasma
Describe the blood supply of the anterior pituitary gland (adenohypophysis)
- No arterial blood supply
- Receives blood through a portal venous system from the hypothalamus
What 4 things does the pituitary gland control?
- Growth (GH)
- Thyroid (TSH)
- Puberty/fertility (LH, FSH)
- Cortisol
Describe the thyroid axis
- Hypothalamus releases TRH (thyrotropin releasing hormone)
- This stimulates the release of TSH (thyroid stimulating hormone) from the anterior pituitary
- This stimulates the thyroid follicular cells to release T3 ad T4
- T3 and T4 feedback to the hypothalamus and pituitary (negative feedback)
If the thyroid gland is removed, will TSH levels increase or decrease?
Increase
If the thyroid is overactive (thyrotoxicosis), will TSH levels increase or decrease?
Decrease
Describe the gonadal axis
- The hypothalamus releases GnRH (gonadotrophin-releasing hormone)
- This triggers the release of LH and FSH from the anterior pituitary
- LH stimulates the release of testosterone from the testis (men) and oestrogen/estradiol (women) from the ovaries to trigger ovulation
- FSH triggers the production of sperm (men) and eggs (women)
- Oestrogen and testosterone feedback at the pituitary and hypothalamus (negative feedback)
Describe what happens to LH, FSH and oestrogen levels at menopause
Ovaries fail and stop secreting oestrogen which causes LH and FSH levels to increase
Describe what happens to gonadotropin levels if people are taking testosterone/anabolic steroids
Gonadotropin levels will decrease
Describe the hypothalamus-pituitary-adrenal (HPA) axis
- Hypothalamus produced CRH (corticotrophin releasing hormone)
- This stimulates the anterior pituitary to release ACTH (adrenocorticotrophic hormone)
- This stimulates the release of cortisol from the adrenal glands
- Cortisol feeds back to the hypothalamus and pituitary (negative feedback)
Describe what happens to the adrenal glands if pateints are taking steroids?
ACTH production is switched off so the release of cortisol is decreased and the adrenal glands are suppressed
Describe the growth hormone (GH)/insulin-like growth factors (IGF-1) axis
- The hypothalamus releases GHRH (growth hormone releasing hormone) and SMS (somatostatin)
- These stimulate the anterior pituitary to release GH (growth hormone)
- This stimulates the release of ILGF-1 (insulin-like growth factor-1) from the liver
- IGF-1 feeds back
Describe the release of prolactin
- Dopamine is secreted from the hypothalamus
- This inhibits prolactin release (inhibitory hormone)
- Prolactin is released from the anterior pituitary gland when dopamine levels are low
Describe what happens to prolactin levels when a patient has a damaged hypothalamus or is taking anti-dopaminergic drugs
Prolactin levels will increase as there is a lack of dopamine to inhibit it
Name 5 diseases of the pituitary
- Benign pituitary adenoma
- Craniopharyngioma
- Trauma
- Sheehan syndrome –> apoplexy
- Sarcoidosis/TB
Describe the effect of benign pituitary adenomas on the pituitary
Can grow bigger and cause damage e.g. by pressing on optic nerves
Describe the effect of craniopharygiomas on the pituitary
Benign tumours that are epithelial in origin. Despite being benign, they can grow large and have cysts
Describe the effect of trauma on the pituitary
Shaking/rupture of the pituitary stalk from trauma can cause hypopituitarism
Describe the effect of Sheehan syndrome on the pituitary (apoplexy)
The pituitary gland may grow (particularly in pregnancy). Extreme blood loss (e.g. during childbirth/post partum bleeds) can cause injury/infarction of the pituitary causing apoplexy
What is apoplexy?
Unconsciousness/incapacity resulting from cerebral haemorrhage or stroke