Endocrinology Flashcards
What is primary adrenal insufficiency (Addison’s) , and what is the most common cause causes?
= when the adrenal glands have been damaged, resulting in reduced cortisol & aldosterone secretion.
- Aetiology
- Autoimmunity → most common
- Infections → TB, CMV
- Short-term steroid use
- Trauma
- Adrenal tumours
- Surgical removal of the adrenal glands
What is secondary adrenal insufficiency, and what causes this?
= the result of inadequate ACTH stimulating the adrenal glands, causing low cortisol release.
- Aetiology
- Tumours → pituitary adenomas
- Surgery to pituitary
- Radiotherapy
- Sheehan’s syndrome
- Trauma
What is tertiary adrenal insufficiency? Describe the pathophysiology
= the result of inadequate corticotropin-releasing hormone (CRH) release by the hypothalamus.
- Usually caused by patients taking long-term steroids (>3 weeks)
- Suppresses the hypothalamus due to negative feedback → when the steroids are withdrawn, the hypothalamus does not wake up fast enough, meaning endogenous steroids are not adequately produced.
- This is why we taper steroid use slowly
What are the symptoms of adrenal insufficiency?
- Often very vague
- Low cortisol
- Fatigue → increases throughout the day
- Muscle weakness & cramps
- Weight loss
- Low aldosterone
- Dizziness & fainting
- Thirst & craving salt
- Abdominal pain
- Low androgens
- Reduced libido & sexual function
- Depression
What are the signs of adrenal insufficiency?
- Increased ACTH
- Bronze hyperpigmentation of the skin, particularly in creases → ACTH stimulates melanocytes to produce melanin. Only in primary adrenal insufficiency.
- Low cortisol
- Low BMI → unintentional weight loss
- Low aldosterone
- Hypotension → postural drop
- Tachycardia
- Low androgens
- Loss of axillary & pubic hair
- Other signs, associated with other autoimmune disorders
- Goitre → hashimoto’s thyroiditis
- Vitiligo
- Dermatitis herpetiformis → coeliac
What investigations are done for suspected adrenal insufficiency?
- Hyponatraemia → key finding
- Other potential blood findings
- Hyperkalaemia
- Hypoglycaemia
- Raised creatinine & urea → due to dehydration
- Hypercalcaemia
- 9am cortisol → low, can be falsely normal
- Autoantibodies may be present → adrenal cortex antibodies, 21-hydroxylase antibodies
Short Synacthen Test:
= the test of choice for diagnosing adrenal insufficiency, it is ideally performed in the morning.
- Give a dose of synthetic ACTH (synacthen), checking the blood cortisol level before, 30 mins after, and then 60 minutes after
- The Synacthen will stimulate healthy adrenal glands to produce cortisol → the level should at least double
What long-term management is given to someone with adrenal insufficiency?
- Patient education, steroid card, ID tag, and emergency letter → ensure that steroid doses are not missed, and doubled during an acute illness.
- Hydrocortisone → cortisol replacement
- Fludrocortisone → aldosterone replacement
- IM hydrocortisone given for emergencies
What is an adrenal crisis, and how does it present?
= an acute presentation of severe adrenal insufficiency where the absence of steroid hormones leads to a life-threatening emergency.
- This may be the initial presentation of adrenal insufficiency or triggered by infection, trauma, or other acute illness in established adrenal insufficiency
Presentation:
- Reduced consciousness
- Severe weakness
- Severe abdominal pain
- Nausea & vomiting
- Hypotension
- Hypoglycaemia
- Hyponatraemia
- Hyperkalaemia
How is an adrenal crisis managed?
- A-E approach
- IM or IV hydrocortisone → 100mg, followed by an infusion or 6hrly doses
- IV fluids
- IV 5% dextrose
- Careful electrolyte monitoring
What do the following results indicate on a radioisotope scan of the thyroid?
1. Diffuse high uptake
2. Focal high update
3. Cold areas
- Diffuse high uptake - graves
- Focal high update - toxic multinodular goitre, adenomas
- Cold areas - thyroid cancer
What is toxic multinodular goitre?
- Due to the development of physiologically active nodules on the thyroid gland, which do not respond to TSH & continuously produce excessive thyroid hormones
- Insidious onset & older patients compared with Graves.
What is De Quervains Thyroiditis?
= when a viral infection causes thyroiditis - presents with thyrotoxicosis initially and a painful neck lump/goitre
What are some signs specific to Graves disease?
- Graves eye disease
- Conjunctival injection
- Aching at the back of the eye
- Diplopia
- Lid retraction
- Lid lag
- Exophthalmos → bulging of the eyes caused by Grave’s disease
- Inflammation, swelling & hypertrophy of the tissue behind the eyeballs force them forward, causing them to bulge out of the sockets
- Pretibial myxoedema
- Waxy, oedematous appearance over the pre-tibial area
- Thyroid acropachy
What do TFTs show for hyperthyroidism?
- Primary (most common)→ low TSH, high T3/4
- Secondary → high TSH, high T3/4
What medication can be given for symptomatic relief in hyperthyroidism?
Beta-blockers -> propranolol
How is hyperthyroidism treated first line (usually)?
Block & Replace:
- Involves blocking the excess thyroid hormone production & replacing it with the correct concentration of exogenous thyroid hormones.
- In most patients with Graves, a block & replace regime can induce remission.
- Blocking → carbimazole
- First line, taken for 12-18 months
- Risks → acute pancreatitis, agranulocytosis
- Replacing → levothyroxine
- Propylthiouracil → 2nd line anti-thyroid. Small risk of severe liver reactions, including death.
What are the rules which must be followed when giving radioactive iodine for hyperthyroidism?
- Women must not be pregnant, breastfeeding, or become pregnant within 6 months of treatment
- Men must not father children within 4 months of treatment
- Limit contact with people after the dose, particularly children & pregnant women
What is a thyroid storm (crisis)? How does it present, and how is it managed?
= a rare complication of thyrotoxicosis which involves excessive adrenergic activity, which can be life threatening.
Clinical Features:
- Palpitations
- Fever
- Confusion/agitation
- Seizures
- Tachycardia
- Nausea & vomiting
- Abdominal pain
Management:
- Admission for monitoring
- Treat similar to any other thyrotoxicosis, but with some additional measures → fluid resuscitation, anti-arrhythmic medication
What will show on TFTs with hypothyroidism?
Primary - high TSH, low T3/4
Secondary - low TSH, low T3/4
What is myxoedema coma?
- = a rare & life-threatening complication of hypothyroidism presenting with altered mental state, hypothermia, bradycardia, and hypoventilation.
- Must be treated rapidly with thyroid replacement therapy, glucocorticoid therapy, and supportive measures.
What is the definition of diabetes insipidus?
= a disease characterised by the passage of large volumes (>3L/24hrs) of dilute urine.
What investigations are done for diabetes insipidus?
- 24hr urine collection
- Plasma glucose → rule out DM
- U&Es → assess renal function, rule out electrolyte abnormalities
- Simultaneous plasma & urine osmolality → low urine osmolality, high/normal serum osmolality
- Urine specific gravity
- Water deprivation test
How does a water deprivation test work, and what do its results show?
- Patient avoids all fluids for up to 8 hours before the test → urine osmolality is then measured.
- If urine osmolality is low, then desmopressin is given → urine osmolality is then measured over the 2-4hrs following this.
- In primary polydipsia → water deprivation will cause urine osmolality to be high, desmopressin does not need to be given.
- In cranial DI → the patient lacks vasopressin. Initially urine osmolality remains low, but the kidneys will respond to desmopressin and then urine osmolality will go high.
- In nephrogenic DI → the patient is unable to respond to vasopressin, so will remain low throughout.
How is neurogenic/cranial diabetes insipidus managed?
- Desmopressin to replace the endogenous deficit.
- Check serum sodium osmolality every 1-3 months
- Overdose results in hyponatraemia
What are the common causes of SIADH?
- Post-operative → after major surgery
- Lung infection → atypical pneumonia & lung abscesses
- Brain pathologies → stroke, TBI, intracranial haemorrhage, meningitis
- Medications → SSRIs, carbamazepine
- Malignancy → SCLC
- HIV
How does SIADH present?
Symptoms:
- Mild hyponatraemia → nausea, vomiting, headache, lethargy, anorexia
- Moderate hyponatraemia → muscle cramps, weakness, confusion, ataxia
- Severe hyponatraemia → drowsiness, seizures, coma
Signs:
- Decreased level of consciousness
- Confusion
- Seizures
- Hypervolaemia → pulmonary oedema, peripheral oedema, raised JVP
How is SIADH managed?
- Hospital admission if symptomatic or severe (Na<125)
- Treat any underlying cause
- Fluid restriction
- Temporarily used to increase sodium concentrations
- 750-1000ml per day
- Correct slowly to prevent osmotic demyelination syndrome & cerebral oedema → <10mmol/L in 24hrs.
- Vasopressin receptor antagonists → tolvaptan
- Block ADH receptors
- Can cause a rapid rise in sodium, and are initiated by an endocrinologist with close monitoring.
