SN6
SHORT NOTE
5M
★ High-yield
Write a short note on Addison disease.
Definition
Addison disease = chronic primary adrenocortical insufficiency, in which both glucocorticoid and mineralocorticoid secretion fail.
Causes
- Autoimmune adrenalitis — commonest in developed countries (70%)
- Tuberculosis — the commonest cause in India
- Metastatic infiltration, amyloidosis, fungal infection
- Adrenal haemorrhage — Waterhouse–Friderichsen syndrome in meningococcaemia
- AIDS-related infections
Clinical Features and Their Basis
| Feature | Mechanism |
|---|---|
| Pigmentation of skin creases, buccal mucosa, scars | Loss of feedback → ↑ ACTH and MSH from POMC. Present only in primary disease |
| Hypotension, postural drop | ↓ Aldosterone → Na+ and water loss; ↓ cortisol → loss of the permissive effect on catecholamines |
| Hyponatraemia, hyperkalaemia, acidosis | ↓ Aldosterone |
| Hypoglycaemia | ↓ Cortisol → ↓ gluconeogenesis |
| Weakness, fatigue, weight loss, anorexia | Combined deficiency |
| Salt craving | Sodium depletion |
| Nausea, vomiting, abdominal pain | Glucocorticoid deficiency |
| Loss of axillary and pubic hair (in women) | ↓ Adrenal androgens |
Primary VS Secondary Insufficiency
| Feature | Primary (Addison) | Secondary (pituitary) |
|---|---|---|
| ACTH | ↑↑ | ↓ |
| Pigmentation | Present | Absent |
| Aldosterone | ↓ | Normal (renin-driven) |
| Hyperkalaemia | Present | Absent |
| Other pituitary hormones | Normal | Often deficient |
Investigations
- Short Synacthen (ACTH stimulation) test — the definitive test; cortisol fails to rise
- Plasma ACTH — high in primary disease
- Electrolytes — low Na+, high K+; blood glucose low
- Imaging or tuberculin testing to establish the cause
Applied Aspects
- Addisonian crisis — precipitated by infection, surgery, trauma or abrupt steroid withdrawal. Severe hypotension, vomiting, hypoglycaemia, shock. A medical emergency — treat with IV hydrocortisone and saline before waiting for confirmatory tests
- Maintenance — hydrocortisone + fludrocortisone for life
- Dose must be doubled during illness or surgery — the "sick day rules"; patients should carry a steroid card
All questions in Endocrine System
- Q1Describe the synthesis, transport and actions of thyroid hormones. Explain the regulation of thyroid secretion. ★
- Q2Describe the source, synthesis, actions and regulation of insulin. Add a note on glucagon. ★
- Q3Enumerate the hormones of the adrenal cortex. Describe the actions and regulation of cortisol and aldosterone. ★
- Q4Describe the actions and regulation of growth hormone. Add a note on the disorders of its secretion. ★
- Q5Describe the regulation of plasma calcium. Explain the actions of parathyroid hormone, vitamin D and calcitonin. ★
- SN1Write a short note on hypothyroidism. Describe cretinism and myxoedema. ★
- SN2Write a short note on Cushing syndrome. ★
- SN3Describe the hormones of the adrenal medulla and their actions. Differentiate adrenaline from noradrenaline. ★
- SN4Write a short note on oxytocin. ★
- SN5Define diabetes mellitus. Give its diagnostic criteria, types and complications. ★
- SN6Write a short note on Addison disease. ★
- SN7Enumerate the thyroid function tests and describe their interpretation.