Endocrinology Flashcards
Describe the thyroid axis.
Hypothalamus releases TRH
Pituitary releases TSH
Thyroid releases T4 mostly and some T3 (T4 is converted to T3 peripherally)
Name 4 functions of thyroid hormone.
Increase heart rate and cardiac output
Increases gut motility
Increase hepatic glucose output
Increase lipolysis
What is the epidemiology of hyperthyroidism?
Much more common in femaes
List the causes of hyperthyroidism
Graves’ Disease - 2/3 of cases
Toxic multinodular goitre
Solitary toxic adenoma
Drug induced - ie. amiodarone or lithium
Describe the pathophysiology of Graves’ Disease
Autoimmune condition. Increase in TSH stimulating antibody which mimics TSH to stimulate thyroid hormone release from the thyroid.
List the symptoms of hyperthyroidism.
Diarrhoea Weight loss Increased appetite Sweats Heat intolerance Palpitations Tremor Anxiety Menstrual disturbance - slow or no periods.
List the signs of hyperthyroidism
Tachycardia Thin hair Goitre Fine tremor Lid lag
What is the specific sign of Graves’ Disease?
Graves’ ophthalmology - swelling of the extra-ocular muscles causes pain and lid retraction.
What are the investigations for suspected hyperthyroidism?
Thyroid function tests - T3, T4 and TSH
Thyroid autoantibodies - TSH receptor stimulating antibodies in Graves’
Iodine uptake scan
What are the results of thyroid function tests in primary hyperthyroidism (problem with the thyroid itself ie. toxic multinodular goitre)
Low TSH, raised T3/T4
What are the results of thyroid function tests in secondary hyperthyroidism (problem with the pituitary ie. pitutary adenoma)
High TSH, raised T3/T4
What are the treatment options for hyperthyroidism?
Block and replace - Carbimazole (anti-thyroid drug), thyroxine (to replace the thyroid hormone)
Radioiodine
Thyroidectomy
What is the treatment for a thyroid storm?
Beta blockers ie. propanolol
What are the complications of hyperthyroidism?
Heart failure Angina Atrial Fibrillation Ophthalmology Thyroid storm
What is the epidemiology of hypothyroidism?
Much more common in women.
What are the causes of hypothyroidism?
Primary atrophic hypothyroidism (autoimmune)
Hashimoto’s thyroiditis (autoimmune - causes goitre)
Iodine deficiency - biggest worldwide cause
Drug induced - amiodarone, lithium
Treatment of hyperthyroidism
What are the symptoms of hypothyroidism?
Constipation Intolerance to cold Weight gain Tired Menstrual disturbance - heavy periods
What are the signs of hypothyroidism?
Bradycardia Cold hands Ascites Goitre Round puffy face
What is the mainstay of investigation for hypothyroidism?
Thyroid function tests
What are the results of thyroid function tests for primary hypothyroidism (problem with the thyroid - ie. Hashimoto’s)
High TSH, Low T3/T4
What are the results of thyroid function tests for secondary hypothyroidism (problem with the pituitary)
Low TSH, low T3/T4
What is the treatment of hypothyroidism?
Give levothyroxine
What is a drug that can interfere with thyroid function?
Amiodarone - iodine rich drug.
What stimulates parathyroid hormone release?
Decrease circulating calcium.
What is the action of parathyroid hormone?
Increase bone resorption of calcium
Increase gut absorption of calcium
Increase kidney reabsorption of calcium
What is the cause of primary hyperparathyroidism?
Solitary adenoma
Diffuse hyperplasia
What is the presentation of hyperparathyroidism?
THINK INCREASED CALCIUM
Weak, tired, depressed, thirsty, renal stones.
Osteoporosis and fracture susceptibility
Increased blood pressure
What investigations should be carried out in hyperparathyroidism?
Serum calcium, PTH and phosphate
What are the serum investigation results in primary hyperparathyroidism?
Raised calcium, raised PTH and low phosphate
What are the causes of secondary hyperparathyroidism?
This is an appropriate response to hypocalcaemia - caused by vit D deficiency or CKD.
What are the causes of tertiary hyperparathyroidism?
Often occurs as a result of longstanding secondary hyperparathyroidism and parathyroid hyperplasia.
What are the serum investigation results in secondary hyperparathyroidism?
Low calcium, high PTH, high phosphate
What are the serum investigation results in tertiary hyperparathyroidism?
High calcium, high PTH, high phosphate
What is the management of hyperparathyroidism?
Increase fluid intake to prevent stones
Give bisphosphonates to support bones
Excision of causative adenoma
Parathyroidectomy
What are the three groups of hormones the adrenal cortex produces and give an example of each.
Glucocorticoids ie. cortisol
Mineralocorticoid ie. aldosterone
Androgens ie. DHEA
What is the axis that stimulates cortisol release from the adrenal gland?
Hypothalamus secreted CRH
Anterior pituitary secretes ACTH
Adrenal glands secrete cortisol
What is the function of cortisol
Many functions - think metabolism regulation.
What is Cushing’s syndrome?
Clinical state of increased free circulating glucocorticoid (cortisol)
What is Cushing’s Disease?
Clinical state of increased free circulating glucocorticoid (cortisol) caused by a pituitary adenoma.
What are the ACTH dependant causes of Cushing’s syndrome?
Pituitary adenoma (ACTH secreting) - Cushing's disease Ectopic ACTH production - ie. small cell lung cancer.
What are the ACTH independent causes of Cushing’s?
Adrenal adenoma
Adrenal hyperplasia
Exogenous steroids!!
What are the symptoms of Cushing’s disease?
Increased weight
Mood change - depression, psychosis
Acne
Muscular weakness
What are the signs of Cushing’s disease?
central obesity Striae Moon face Glycosuria Skin and muscle atrophy
What investigations do you carry out in suspected Cushing’s?
24-hour dexamethasone test - is dexamethasone does not suppress cortisol levels then Cushing’s likely/
24-hour urinary free cortisol - if normal Cushing’s is unlikely.
Why do you not carry out a random plasma cortisol test in Cushing’s?
Cortisol varies according to a circadian rhythm, stress and illness can influence levels also.
What is the treatment of iatrogenic Cushing’s?
Stop steroids if possible
What is the treatment of Cushing’s disease?
Surgical removal of pituitary adenoma.
What is the treatment of adrenal adenoma Cushing’s?
Surgical removal or radiotherapy.
What is Nelson’s syndrome?
A syndrome often caused by adrenalectomy, where there is no cortisol produced and so a build up of ACTH. causes bronze pigmentation, visual disturbances and headaches.
What is Addison’s disease?
This is a form of autoimmune primary adrenal insufficiency
What are the causes of primary adrenal insufficiency?
Autoimmune - Addison’s
TB
Adrenal metastases
What is the the most common worldwide cause of adrenal insufficiency?
TB
What are the symptoms of Addison’s disease?
Weight loss Tiredness Low mood Nausea and vomiting 'tanned, tired, toned, tearful'
What are the signs of Addison’s disease?
Bronze pigmentation - Nelson’s syndrome due to ACTH build up.
High potassium and low sodium (due to low aldosterone)
Low glucose (due to low cortisol)
Postural hypotension (low aldosterone)
Muscle wasting
Investigation sin Addison’s disease?
Blood tests show -
High potassium and low sodium (due to low aldosterone)
Low glucose (due to low cortisol)
Adrenal autoantibody tests
ACTH stimulation test - cortisol will be low.
What is the management of Addison’s disease?
Replace steroids - hydrocortisone
Replace aldosterone - fludrocortisone
How does someone in an Addison’s crisis present?
Shock, fluid loss, severe hypotension, loss of consciousness
How do you treat an Addison’s crisis?
Steroids and fluids ASAP.
What is the cause of secondary adrenal insufficiency?
Long term steroids can suppress the pituitary-adrenal axis - so on withdrawal of steroids the adrenals no longer produce cortisol (aldosterone still produced).
What is Conn’s syndrome?
Excess production of aldosterone caused by an aldosterone producing adenoma.
What is primary hyperaldosteronism?
Excess production of aldosterone independent of RAAS, causing sodium and water retention and decreased renin release.
What is the function of aldosterone?
Increase sodium (and water) retention and increase potassium excretion in the kidneys –> maintenance of blood pressure.
What are the causes of hyperaldosteronism?
Conn’s syndrome - aldosterone producing adenoma
Bilateral adrenal hyperplasia
What are the symptoms of hyperaldosteronism?
Either asymptomatic or liked to hypokalaemia: Weakness Cramps Constipation Paraesthesia Polyuria Polydypsia
What are the signs of hyperaldosteronism?
Hypertension (sometimes)
Hypokalaemia (sometimes)
What are the investigations for suspected hyperaldorsteronism?
Plasma aldosterone - raised
Plasma renin - low
U+E - hypokalaemia
What is the treatment of Conn’s syndrome?
laparoscopic adrenalectomy
What are the medical treatments of hyperaldorseronism?
Spinonolactone - this is a direct aldosterone antagonist
What is acromegaly?
Increased production of growth hormone in adults after fusion of the epiphyseal growth plates.
What is gigantism?
Increased production of growth hormone occurring in children.
What is the cause of acromegaly?
GH secreting pituitary tumour (99%)
pituitary hyperplasia
What is the growth hormone axis?
GHRH is secreted from the hypothalamus
GH is secreted from the anterior pituitary
GH acts on its target tissues