Endocrinology Flashcards
Adrenal insufficiency/Addison’s definition
Adrenal glands do not produce enough steroid hormones (cortisol & aldosterone)
Addison’s disease = primary adrenal insuff. caused by autoimmunity
Primary adrenal insufficiency definition
Adrenal glands damaged, resulting in low cortisol and aldosterone secretion (inc. Addison’s; specifically autoimmune)
Secondary adrenal insufficiency definition
Inadequate ACTH resulting in a lack of stimulation of adrenal glands
Result of loss of/damage to pituitary from pituitary adenoma, surgery, radiotherapy or trauma
Tertiary adrenal insufficiency definition
Insufficient CRH release from hypothalamus
Usually from patients on long-term (>3 weeks) steroids not tapering doses correctly
Adrenal insufficiency presentation
Fatigue
Muscle weakness
Muscle cramps
Dizziness and fainting
Thirst and craving salt
Weight loss
Abdominal pain
Depression
Reduced libido
Bronze hyperpigmentation of the skin, particularly in creases (ACTH stimulates melanocytes to produce melanin)
Hypotension (particularly postural hypotension – with a drop of more than 20 mmHg on standing)
Adrenal insufficiency investigations
Hyperkalaemia (high potassium)
Hypoglycaemia (low glucose)
Raised creatinine and urea due to dehydration
Hypercalcaemia (high calcium)
Early morning cortisol often falsely low
ACTH measured directly may be high or low depending on primary/secondary/tertiary
Adrenal cortex or 21-hydroxylase antibodies may be present in Addison’s
CT or MRI of adrenal glands or MRI of pituitary may be helpful
Test for adrenal insufficiency
Short synacthen test
Synthetic ACTH given & cortisol checked after 30 and 60 minutes
Should double cortisol levels
If failure to double, either primary adrenal insufficiency or significant adrenal atrophy from prolonged secondary adrenal insufficiency
Management of adrenal insufficiency
Hydrocortisone to replace cortisol
Fludrocortisone to replace aldosterone if needed
When ill, double hydrocortisone dose to mimic body’s response to stressors, and attend A&E if vomiting
Will have medical ID bracelet and steroid card, and should carry emergency hydrocortisone injection
Adrenal crisis definition, presentation & management
Acute presentation of severe adrenal insufficiency
Present with:
Reduced consciousness
Hypotension
Hypoglycaemia
Hyponatraemia and hyperkalaemia
Manage with IV hydrocortisone, IV fluids, IV dextrose
ABCDE approach to management
Hyperthyroidism definition
Over-production of thyroid hormones, T3 & T4 by thyroid gland
Thyrotoxicosis definition
Effects of an abnormal/excessive amount of thyroid hormones on the body
Primary hyperthyroidism definition
Dysfunction of the thyroid gland itself, producing excessive thyroid hormone e.g. Grave’s disease, in which autoantibodies stimulate TSH receptors
Secondary hyperthyroidism definition
Dysfunction of the pituitary or hypothalamus and over-production of TSH e.g. from a pituitary adenoma
Sub-clinical hyperthyroidism definition
Thyroid hormones (T3/T4) are normal but TSH is suppressed/low
(May have mild or absent symptoms)
Grave’s disease definition
Form of primary hyperthyroidism in which anti-TSH receptor antibodies bind to the receptors on the thyroid and stimulate excessive thyroid hormone secretion
Plummer’s disease definition
Form of primary hyperthyroidism in which nodules develop on the thyroid gland which are unregulated by the thyroid axis and continually secrete thyroid hormones
(Most common in patients >50 years old)
Grave’s disease presentation
In addition to the universal symptoms of hyperthyroidism
Also present with Grave’s eye disease, which is evident via lid lag and exophthamos
Pretibial myxoedema (gives skin a discoloured, waxy, oedematous appearance)
Goitre
Hyperthyroidism presentation
Anxiety and irritability
Sweating and heat intolerance
Tachycardia
Weight loss
Fatigue
Insomnia
Frequent loose stools
Sexual dysfunction
Brisk reflexes on examination
Thyroid storm presentation and management
Acute presentation of hyperthyroidism
Presents with fever, tachycardia and delirium
symptomatic treatment e.g. paracetamol
treatment of underlying precipitating event
beta-blockers: typically IV propranolol
anti-thyroid drugs: e.g. methimazole or propylthiouracil
Lugol’s iodine
dexamethasone/hydrocortisone - blocks the conversion of T4 to T3
Hyperthyroidism management & drug contraindications
Carbimazole = first line drug
Propylthiuracil = second line drug
(Both can cause agranulocytosis, if suffering sore throat stop taking and see a doctor ASAP
Carbimazole is contraindicated in pregnancy)
Propranolol for symptomatic relief
Radioactive iodine can be used as a definitive treatment
Hyperparathyroidism definition
Overactivity of the 4 parathyroid glands, resulting in excessive secretion of PTH
Hyperparathyroidism presentation
Bones, moans, stones & groans
(bone pain, depression, delirium, kidney stones, abdominal moans [vomiting, nausea and constipation])
Categorised by hypercalcaemia
Primary hyperparathyroidism definition, biochem presentation and management
Uncontrolled PTH release from the parathyroid glands e.g. from a tumour
Presents with elevated PTH and calcium
Manage surgically
Secondary hyperparathyroidism definition, biochem presentation and management
Insufficient vitamin D or chronic kidney disease reduces calcium absorption, leading to hypocalcaemia
Presents with elevated PTH but low/normal calcium
Treat by correcting underlying condition
Tertiary hyperparathyroidism definition, biochem presentation and management
Caused by hyperplasia of the parathyroid gland due to prolonged secondary hyperparathyroidism post-resolution
Presents with high PTH and high calcium
Treat by surgically removing part of parathyroid tissue
Hypothyroidism definition
Insufficient thyroid hormones, T3 & T4
Primary hypothyroidism definition & biochem
Thyroid behaves abnormally and produces inadequate thyroid hormones e.g. iodine deficiency
Loss of negative feedback, hence presents with elevated TSH
Secondary hypothyroidism definition & biochem
Secondary hypothyroidism is often associated with a lack of other pituitary hormones, such as ACTH, referred to as hypopituitarism. This is rarer than primary hypothyroidism, and may be caused by:
Tumours (e.g., pituitary adenomas)
Surgery to the pituitary
Radiotherapy
Sheehan’s syndrome (where major post-partum haemorrhage causes avascular necrosis of the pituitary gland)
Trauma
Low TSH, Low T3/4
Hashimoto’s thyroiditis definition
Autoimmune condition associated with anti-TPO and anti-Tg
Causes goitre followed by wasting/atrophy of thyroid gland
Hypothyroidism management
Oral levothyroxine = first-line treatment (synthetic T4)
Liothyronine sodium = rarely used under specialist care (synthetic T3)
Hypothyroidism presentation
Weight gain
Fatigue
Dry skin
Coarse hair and hair loss
Fluid retention (including oedema, pleural effusions and ascites)
Heavy or irregular periods
Constipation
Goitre for iodine deficiency
Cushing’s syndrome & disease definition
Refers to prolonged high levels of glucocorticoids in the body (primarily cortisol)
Cushing’s disease refers specifically to high levels from a pituitary adenoma secreting excessive ACTH
Cushing’s syndrome presentation
Round face (known as a “moon face”)
Central obesity
Abdominal striae (stretch marks)
Enlarged fat pad on the upper back (known as a “buffalo hump”)
Proximal limb muscle wasting (with difficulty standing from a sitting position without using their arms)
Male pattern facial hair in women (hirsutism)
Easy bruising and poor skin healing
Hyperpigmentation of the skin in patients with Cushing’s disease
Causes of Cushing’s mnemonic
CAPE
Cushing’s disease
Adrenal adenoma
Paraneoplastic syndrome (ACTH from tumour somewhere other than pituitary)
Exogenous steroids
Cushing’s syndrome diagnostic test
Dexamethasone suppression test
First line = low dose overnight test, give dexamethasone at 11pm and check cortisol at 9am - suppressed normally
For the low-dose 48-hour test, dexamethasone (0.5mg) is taken every 6 hours for 8 doses, starting at 9 am on the first day. Cortisol is checked at 9 am on day 1 (before the first dose) and 9 am on day 3 (after the last dose). A normal result is that the cortisol level on day 3 is suppressed. Failure of the dexamethasone to suppress the day 3 cortisol could indicate Cushing’s syndrome, and further assessment is required.
The high-dose 48-hour test is carried out the same way as the low-dose test, other than using 2mg per dose (rather than 0.5mg). This higher dose is enough to suppress the cortisol in Cushing’s syndrome caused by a pituitary adenoma (Cushing’s disease), but not when it is caused by an adrenal adenoma or ectopic ACTH.
Cushing’s syndrome management
Trans-sphenoidal (through the nose) removal of pituitary adenoma
Surgical removal of adrenal tumour
Surgical removal of the tumour producing ectopic ACTH (e.g., small cell lung cancer), if possible
Hyperaldosteronism/Conn’s syndrome definition
Refers to high levels of aldosterone
Conn’s specifically refers to an adrenal adenoma producing too much aldosterone
May be present in 5-10% patients with hypertension
Primary hyperaldosteronism definition and causes
Adrenal glands directly responsible for producing too much aldosterone
Serum renin will be low due to negative feedback
May be due to a bilateral adrenal hyperplasia, adrenal adenoma (aka Conn’s) or familial
Secondary hyperaldosteronism definition and causes
Caused by excessive renin stimulating the release of excessive aldosterone
Usually due to disproportionately lower blood pressure in the kidneys e.g. renal artery stenosis, liver cirrhosis, heart failure
Hyperaldosteronism biochem & investigatons
High aldosterone
Low renin (primary) or high renin (secondary)
Hypertension
Hypokalaemia
Alkalosis
Adrenal vein sampling
CT/MRI