The Glucocorticoid Axis

Question 1

Describe the adrenal glands?

Answer 1

1. Outer cortex producing cortisol, aldosterone and androgens
2. Inner medulla secreting catecholines

Question 2

Describe the adrenal glands?

Answer 2

1. Outer cortex producing cortisol, aldosterone and androgens
2. Inner medulla secreting catecholines

Question 3

How is cortisol released?

Answer 3

1. Corticotrophin releasing hormone (CRH) from the hypothalamus stimulates ACTH from the anterior pituitary.
2. This stimulates cortisol production from the adrenal glands.
3. Cortisol feeds back to the hypothalamus and pituitary to suppress further CRH/ACTH release

Question 4

Describe Addison’s disease: primary hypoadrenalism?

Answer 4

1. 90% of cases arise from adrenal cortex destruction by organ specific auto antibodies
2. Associated with other autoimmune conditions:
   - autoimmune thyroid disease
   - ovarian failure
   - pernicious anaemia
   - type 1 diabetes mellitus

Question 5

What are the clinical features of Addison’s?

Answer 5

1. Lethargy, depression, anorexia
2. Postural hypotension caused by salt and water loss is an early sign
3. Hyperpigmentation due to stimulation if melanocytes by xs ACTH

Question 6

What are the appropriate investigations for Addison’s disease

Answer 6

1. Single cortisol measurement - random daytime cortisol below 100nmol/l suggestive above 550 makes diagnosis unlikely

Question 7

What are the appropriate investigations for Addison’s disease?

Answer 7

1. The short ACTH test over 30 mins tests if ACTH raises cortisol levels
2. Measure plasma ACTH levels: a high level with low or low/normal levels confirms primary hypoadrenalism
3. Long ACTH test detects secondary hypoadrenalism and steroid suppression

Question 8

What is the management for Addison’s disease?

Answer 8

1. Hydrocortisone: 20mg morning, 10mg evening

2. Fludrcortisone: 50-300mcgs

Question 9

Describe secondary hypoadrenalism?

Answer 9

1. May arise from hypothalamic-pituitary disease or from long term steroid therapy
2. Clinical features same as Addison’s but no pigmentation as ACTH levels are low
3. A long ACTH will differentiate between primary and secondary hypoadrenalism

Question 10

Describe Cushing’s syndrome?

Answer 10

1. Persistently and innappropriately elevated glucocorticoid levels.
2. Most cases result from administration for other conditions
3. Spontaneous Cushing’s can result from xs ACTH secretion

Question 11

Describe the clinical features of Cushing’s?

Answer 11

1. Obese, fat distribution is central, affecting the trunk, abdomen and neck
2. Moon face, skin bruising, striations, pigmentation