Endocrinology Flashcards
What are the three main causes of Addison’s disease
- Autoimmune (more developed countries)
Tuberculosis (more common worldwide)
May also be caused by metastases (eg. bronchial carcinoma)
What are the clinical features of Addison’s disease
- Fatigue
- Abdominal Pain
- Weight Loss
- Hyperpigmentation → -ve feedback causes increased ACTH leading to increased POMC, leading to increased α-MSH
- Nausea, Vomiting, Hypotension
- Hypoglycaemia → may cause dizziness and falls
What are the clinical features of Addisonian Crisis
severe hypovolaemia and hyponatraemia
What are the investigations for Addison’s disease
Short Synacthen test
Morning Serum Cortisol → If short synacthen test unavailable
- Serum Electrolytes (Due to Aldosterone Deficiency) → hyponatraemia + hyperkalaemia
- Hypoglycaemia
- Metabolic Acidosis with normal anion gap
- FBC → anaemia
What are the managements for Addison’s disease
Stable (Glucocorticoid + Mineralocorticoid) → Hydrocortisone (given in 2 or 3 divided doses) + Fludrocortisone
Intercurrent Illnesses ⇒ hydrocortisone (glucocorticoid) dose should be doubled and fludrocortisone dose should stay the same.
What are the managements for Addisonian Crisis
- Addisonian Crisis → IV hydrocortisone, Fluid Resusitation, Glucose (if hypoglycaemia)
- Precipitated by sudden withdrawal of steroids, illness or surgery.
What are the main causes of Cushing’s Syndrome
ACTH Dependent (80%)
- excess ACTH from pituitary adenoma (Cushing’s Disease) (most common endogenous cause)
- ectopic ACTH (Small Cell Lung Cancer)
ACTH Independent (20%)
- Adrenal adenoma
- Adrenal carcinoma
What are the risk factors of Cushing’s Syndrome
exogenous corticosteroid use (most common cause overall), pituitary or adrenal adenoma, or adrenal carcinoma
What are the clinical features of Cushing’s Syndrome
- Thin, easily bruisable skin with ecchymoses
- Stretch marks (striae)
- Proximal Myopathy (Muscle Weakness)
- Central Adiposity
- Fatigue
- Hirsutism, Acne
- Hyperpigmentation (if ACTH dependent)
- Lethargy & Depression
- Osteopenia & Osteoporosis
- Hypertension, Hyperglycaemia
- Increased susceptibility to infection
What are the investigations for Cushing’s Syndrome
- Low Dose (1mg) overnight dexamethasone suppression test → most sensitive and 1st line test. Patients with Cushing’s syndrome do not have their morning cortisol spike suppressed.
- 24-hour urinary free cortisol or Late-night salivary cortisol → elevated
What test distinguishes between Cushing’s disease and ectopic ACTH production
-
High Dose dexamethasone suppression test
- Cushing’s Disease (Pituitary Adenoma) ⇒ will suppress cortisol in high dose dexamethasone suppression test.
As excess ACTH production from the pituitaries can be inhibited by high doses of dexamethasone, however autonomous cortisol production from the adrenals will not be affected
What re the blood results for someone with Cushing’s Syndrome?
- Bloods → Hyperglycaemia, Hypokalaemia, Hypernatraemia, Metabolic Alkalosis (due to increased H+ excretion and bicarbonate reabsorption)
- Ectopic ACTH production (ie. due to small cell lung cancer) is associated with very low potassium levels.
What is the management for Cushing’s Syndrome
- If Iatrogenic → discontinue steroids or use lower dose
- Medical → metyrapone or ketoconazole (inhibit cortisol synthesis)
- Surgical → transsphenoidal pituitary adenomectomy (if pituitary tumour), adrenalectomy (if adrenal adenoma or carcinoma)
What is Diabetes Insipidus
Condition in which kidneys are unable to concentrate urine due to inadequate secretion or sensitivity to ADH, resulting in the production of large quantities of dilute urine
What are the causes for Diabetes Insipidus
Central DI (More common)
insufficient levels of ADH from posterior pituitary.
- Causes = pituitary tumour/surgery, traumatic brain injury, infection (meningitis), sarcoidosis, TB, SAH, hereditary haemochromatosis
Nephrogenic DI → defective ADH receptors in the distal tubules and collecting ducts.
- Causes = lithium therapy, electrolyte imbalances (hypercalcaemia or hypokalaemia), idiopathic, inherited (AVP2 gene)
What are the clinical features for DI
- Polyuria → with very dilute urine
- Nocturia → restless sleep, daytime sleepiness
- Polydipsia → excessive thirst
- Dehydration → tachycardia, reduced tissue turgor, dry mucous membranes
(No symptoms suggestive of DM)
What is the first line investigation to confirm DI?
- Water Deprivation Test → confirmatory test. If osmolality corrects itself then may be psychogenic polydipsia.
If not, after 8 hours administer desmopressin to differentiate between CDI and NDI.
Urine osmolality will rise in CDI but remain low in NDI.
What are other investigations for DI
- Low urine osmolality + High serum osmolality
- Hypernatraemia and Hypokalaemia
MRI → look for brain/pituitary tumour
- If Low Sodium → psychogenic polydipsia (in context of low urine osmolality)
- Normal blood glucose → exclude DM
What is the management for DI
-
Hypernatraemia → manage with oral or IV fluids (prevent dehydration)
- Correction of chronic hypernatraemia too fast predisposes to cerebral oedema
- Central DI → intranasal Desmopressin
- Nephrogenic DI → discontinue causative agent if medication induced (lithium), Thiazide Diuretics, sodium restriction
What genetic component is T1DM most strongly associated with?
Associated with HLA DR3/4.
What are the clinical features for both T1DM and T2DM
- Polyuria and Polydipsia
- Polyphagia (Excessive Appetite)
- Unexplained Weight Loss
- Fatigue
- Increased Susceptibility to Infections
- Acanthosis Nigracans (hyperpigementation) → T2DM
What is the first presentation in 1/3 of T1DM cases
DKA is first manifestation in around 1/3 of cases.
N&V, abdominal pain, kussmaul breathing, sweet smelling breath.
What are the investigations for DM
Measuring Blood Glucose
- finger-prick, one-off blood glucose (fasting or non-fasting)
- HbA1c (average blood glucose over last 2-3 months
-oral glucose tolerance test (measurement of glucose 2 hours after consumption of 75g of glucose)
C-Peptide (distinguish type 1 vs type 2) → decreased in type 1, increased in type 2
Urinalysis (Urine Dip)
- glucosuria
- ketone bodies (T1DM)
-microalbuminuria (early signs of nephropathy)
Antibodies in T1DM → Anti-GAD Antibodies and Islet Cell Antibodies
What is the diagnostic criteria for DM
Symptomatic
- **fasting glucose ≥7.0mmol/L** - OR **random glucose ≥11.1mmol/L**
Asymptomatic → above criteria must be demonstrated twice (on two separate days)
HbA1c ≥48 mmol/mol
- 42-47 is pre diabetic
What is the management plan for T1DM?
Basal-Bolus Insulin ⇒
long acting (eg. insulin glargine, subcutaneous injection OD)
+ short acting (eg. insulin lispro or aspart, before meals)