Ramzi Ajjan's Intro to Endocrinology from IMS

Question 1

What is the main functional difference between the anterior and posterior pituitary?

Answer 1

Anterior - produces hormones

Posterior - stores hormone

Question 2

Which hormones are produces by the anterior pituitary?

Answer 2

Growth hormone (GH)
- For skeletal growth

Adrenocorticotrophic hormone (ACTH)
- Stimulates the adrenals to produce steroids

Gonadotrophins (FSH and LH)
- Stimulate the testicles or ovaries to produce sex hormones

Thyroid stimulating hormone or thyrotrophin (TSH)
- Stimulates the thyroid to produce thyroid hormones

Prolactin (PRL)
- Stimulates breast milk production

Question 3

Which hormones are stored in the posterior pituitary?

Answer 3

Those produced by the the hypothalamus:

Antidiuretic hormone (ADH)
- Stimulates water reabsorption by the kidneys

Oxytocin
- Helps uterine contractions during labour

Question 4

Which part of the brain controls the anterior pituitary?

Answer 4

The hypothalamus

Question 5

What hormones are produced by the hypothalamus to control the anterior pituitary?

Answer 5

• Corticotrophin releasing hormone (CRH): stimulates ACTH secretion
• Growth hormone releasing hormone (GHRH): stimulates GH secretion
• Thyrotropin releasing hormone (TRH): stimulates TSH secretion
• Gonadotrophin releasing hormone (GnRH): stimulates FSH and LH secretion
• Prolactin releasing hormone does not exist and prolactin is under the inhibitory effect of the hypothalamus

Question 6

How are pituitary hormones ‘switched off’?

Answer 6

• Cortisol switches off ACTH and CRH
• Growth hormone, switches off GH and GHRH
• Thyroid hormones switch off TSH and TRH
• Sex hormones switch off FSH/LH and G

Question 7

Which glands are not controlled by the pituitary?

Answer 7

Adrenal medulla
- Produce adrenaline and noradrenaline

Parathyroid
- Controls calcium levels

Pancreas
- Controls sugar levels

Gut hormones

Question 8

Describe the anatomy of the adrenal glands.

Answer 8

Adrenal cortex, 90% of the gland and produces:

• Cortocosteroids (cortisol)
• Androgens (male hormones)
• Mineralocorticoid (aldosterone)

Adrenal medulla, 10% of the gland and produces:
- Catecholamines (adrenaline, noradrenaline and dopamine)

Question 9

Is catecholamine secretion controlled by the pituitary?

Answer 9

Catecholamine secretion is not controlled by the pituitary (related to blood pressure)

Question 10

Is mineralcorticoid secretion controlled by the pituitary?

Answer 10

No - related to renin-angiotensin system, which controls the blood pressure.

Question 11

What are the possible clinical abnormalities of endocrine glands\/

Answer 11

Hormonal oversecretion

• Primary
• Secondary

Hormonal undersecretion

• Primary
• Secondary

Tumour/nodules in the gland without affecting hormone secretion

Question 12

What are static tests used for?

Answer 12

Can diagnose abnormalities of thyroid and sex glands. For example:

In those with primary hyperthyroidism (thyroid hormone overproduction), we can test for

• Thyroid hormones (T3 and T4)
• TSH

If primary hyperthyroidism is present then T3 and/or T4 is elevated with suppressed (undetectable) TSH

Question 13

What are stimulation tests used for?

Answer 13

For suspected hormonal under-secretion where a static test is not enough.

Question 14

What is the synacthen test?

Answer 14

• Giving ACTH to test for adrenal insufficiency

- If an individual fails to respond to a stimulation test then gland failure is diagnosed

Question 15

What is the insulin stress test?

Answer 15

0 minutes:
- take 3 mL blood in plain tubes for GH, cortisol and 1 mL in fluoride tube for glucose and inject insulin iv.

30,45,60,90,120 min:
- take 3 mL blood in plain tubes for GH, cortisol and 1 mL in fluoride tube for glucose.

Adequate hypoglycaemia ( 400 nmol/L may only need steroid cover for major illnesses or stresses. 
- An adequate GH response occurs with an absolute response > 20 mU/L (7µg/L).

Cushing’s syndrome:
- There will be a rise of less than 170 nmol/L above the fluctuations of basal levels of cortisol.

Question 16

What is the glucagon stimulation test?

Answer 16

0 min - take 2 mL blood into plain tube for cortisol & GH
immediately give Glucagon intra-muscularly.

150 min - take 2 mL blood into plain tube for cortisol & GH

180 min - take 2 mL blood into plain tube for cortisol & GH

An adequate cortisol response is defined as a rise of greater than 200 nmol/L to above 600 nmol/L.

Question 17

What are suppression test used for?

Answer 17

Hormonal over-secretion.

Examples include:

• Giving steroids and testing for endogenous steroid production (external steroids should switch off internal steroid production)
• Giving glucose and testing GH secretion (glucose switches off GH secretion in normal individuals)

Question 18

What kind of test would be used in the diagnosis of growth hormone oversecretion (gigantism, acromegaly)?

Answer 18

Suppression test

Glucose is given, followed by GH measurements at different time points. In healthy individuals, glucose suppresses GH production and hence plasma levels of the hormones fall but not in those with oversecretion.

Question 19

What kind of test would be required to confirm a diagnosis of Cushing’s disease (excess cortisol)?

Answer 19

Supression test

Dexamethasone suppression test is used to confirm the failure to suppress endogenous cortisol production.

Question 20

Is a static test enough to diagnose hyperthyroidism?

Answer 20

Yes

Thyroid blood test:

• Raised thyroid hormone
• Suppressed TSH

Question 21

What tests may be used in the diagnosis of growth hormone deficiency?

Answer 21

• Glucagon stimulation test

- Insulin stress test

Question 22

How is hypothyroidism diagnosed?

Answer 22

Static test of thyroid function