Endocrinology 2

Question 1

What is the difference between primary hypothyroidism and secondary hypothyroidism? How does this effect the TSH, T4 and T3 levels?

Answer 1

Primary hypothyroidism - The defect is in the pituitary gland. This means that there is low T4 and T3 levels but TSH levels are very high. This is due to negative feedback.

Secondary hypothyroidism: The defect is in the pituitary gland. As a result TSH levels are low, meaning the T3 and T4 level are low.

Question 2

What is the difference between primary hyperthyroidism and secondary hyperthyroidism? How does this effect the TSH, T4 and T3 levels?

Answer 2

Primary hyperthyroidism - The defect is in the pituitary gland. This means that there is high T4 and T3 levels but TSH levels are very low - undetectable. This is due to negative feedback.

Secondary hyperthyroidism: The defect is in the pituitary gland. As a result TSH levels are very high, meaning the T3 and T4 level are high.

Question 3

What can a static test diagnose?

Answer 3

• Thyroid defects e.g. hyperthyroidism and hypothyroidism
• Sex hormone defects
• Prolactin levels

Question 4

What test is used to determine Adrenal insufficiently?

Answer 4

Synacthen Test

Give ACTH and cortisol levels should increase. This is a type of stimulation test.

Question 5

What tests can we use to test the pituitary gland?

Answer 5

Insulin stress test - give insulin and cause people to become hypoglycaemic. This is a very stressful condition for the body. Cortisol and GH levels should increase. Can be dangerous for people as it can cause a heart attack.

Glucagon stimulation test - Give glucagon. The levels of Cortisol and GH levels should increase. If not, this suggest pituitary failure. The results can be equivocal.

Question 6

How do you test for cortisol over production? How do you test for GH over production?

Answer 6

Give them a high dose of oral cortisol - dexamethasone - the cortisol production should switch off. This test checks for Cushing’s syndrome. In this condition, large amounts of cortisol are produced by the adrenal glands.

For GH, give them glucose. This should cause and decrease in GH secretion. If it does not switch off, it can lead to acromegaly.

Question 7

Make a diagnosis 1: 
Static test
Patient 1: 
Free T4 53.2 pmol/L (normal range 10-20)
TSH <0.05mIU/L (normal range 0.2-4.0)

Patient 2:
Free T4 5.4 pmol/L
TSH 38 mIU/L

Answer 7

Patient 1: Primary hyperthyroidism

Patient 2: Primary hypothyroidism (The pituitary is producing more TSH to cause the thyroid to increase T4 levels)

In both cases TSH levels are normal

Question 8

Make a diagnosis 3: 
Static test
Patient 3: 
Free T4 39.1 pmol/L (normal range 10-20)
TSH 11. 2 mIU/L (normal range 0.2-4.0)

Patient 2:
Free T4 5.9 pmol/L
TSH 1.1 mIU/L

Answer 8

Patient 3: Secondary hyperthyroidism
There is an inappropriate high TSH

Patient 4:
Secondary Hypothyroidism

It is secondary as the TSH levels should be higher - the pituitary is not compensating.

Question 9

Make a diagnosis 4: 
Static test
Patient 4: 
27 year old gentlemen with sexual dysfunction
Testosterone 4.1 nmol/L (normal 12-28) 
FSH 1.1 IU/L 
LH 0.9 IU/L 
These values are low

Answer 9

Secondary Testicular Failure

The FSH and LH levels are inappropriately low - should be very high to increase testosterone levels

Question 10

Make a diagnosis 5:
A 31 year old lady with suspected adrenal failure. She has lost weight, nausea, vomiting and low blood pressure.

Synacthen Test (inject ACTH at 0 min)
0 min - Cortisol 75 nmol/L
30 min - Cortisol 110 nmol/L (expected > 580)

Answer 10

Adrenal

To be able to tell if it is primary of secondary you can do an ACTH test. If is high it is primary.

Question 11

Make a diagnosis 6:
A 50 year old man with suspected cortisol over production (Cushing’s syndrome)

Dexamethasone suppression test
Morning cortisol: 350 nmol/L (expected < 50)

Answer 11

He has Cushing’s syndrome

Question 12

What are the causes of diseases of endocrine glands?

Answer 12

• Over-secretion can be due to begin tumour

Under secretion due to:

• Inflammation
• Infarction

Tumours/ Nodules with normal hormone production

Question 13

What is the clinical presentation of prolactin over-secertion? What is the most common cause?

Answer 13

• Galactorrhea (breast-milk production)
• Amenorrhoea in women
• Sexual dysfunction in males as there is suppression of FSH and LH production
• Headaches and visual field problems if the tumour is large

Prolactinoma - Prolactin secreting tumour

Question 14

What is the clinical presentation of prolactin over-secertion? What is the most common cause?

Answer 14

• Galactorrhea (breast-milk production)
• Amenorrhoea in women (if levels are not very high it present as irregular periods)
• Sexual dysfunction and decrease in libido in males as there is suppression of FSH and LH production
• Headaches and visual field problems if the tumour is large

Prolactinoma - Prolactin secreting tumour
Static test is always enough but you usually do an MRI also.

Question 15

What are the other causes of mildly raised prolactin? What is the treatment?

Answer 15

• Nipple stimulation
• Stress
• Sexual intercourse
• Drugs (including antipsychotics and antidepressants)
• Non-functioning pituitary tumour

Most you can treat medically - unlike other pituitary tumours

Question 16

What is the presentation of GH overscretion?

Answer 16

Children or adolescent growth hormone excess:

• Excessive growth spurt and increased size of feet and hands - acromegaly
• Can lead to gigantism

Adults:

• increased sweating
• coarse facial features

GH over secretion is usually due to a pituitary tumour. GH secreting tumours are removes surgically - it. is accessed through the nose. After which radiotherapy and medical therapy are used.

Question 17

What is Cushing’s syndrome? What are the possible causes?

Answer 17

Rare syndrome. Leads to the over-production of Cortisol. Can be due to a:

• Pituitary ACTH tumours (then it is caused Cushing’s disease)
• Adrenal tumours secreting cortisol (if due to adrenal pathology cause low ACTH due to negative feedback)
• Cancers producing an ACTH like substance - such as lung cancers

Question 18

What is the clinical presentation of Cushing’s syndrome? How do you test for it? How do you treat it?

Answer 18

Children stop growthing. In adults moon-like face, acne, hirsutism, fat re-distribution (think extremities and central obesity), thin skin leading to scarring, poor wound healing, diabetes etc.

Dexamethasone test. Cortisol levels after this treatment should be low.

To differentiate between Adrenal and Pituitary Cushing’s Syndrome, do a ACTH test. If Adrenal, the ACTH level is undetectable. If Pituitary related, the ACTH levels will be very high. Treatment is surgical with radiotherapy/medical treatment.