DFTs

Question 1

What are dynamic function tests?

Answer 1

In testing for the function of specific endocrine organs following an abnormal hormonal level

Question 2

What two types of DFT exist

Answer 2

Stimulation and suppression

• Stimulation provokes the release of a hormone
• suppression test prevent hypothalamic release

Question 3

What is the short synachten test used for?

Answer 3

Assess the function of adrenal glands stress response by measuring the cortisol response to injected synthetic ACTH (tetracosactrin)

Question 4

Physiological response in short synachten test

Answer 4

Rapid rise in serum cortisol

- Adrenal insufficiency indicated if there is no change or inadequate change

Question 5

What is the short synacthen protocol? and cautions?

Answer 5

1. Collect baseline serum sample at 9am
2. Administer 250ug synachten i.v
3. Second serum sample 30min later, and 60min
4. Adrenal insufficiency is excluded by 30min if value >430nmol/L (Roche)

• Not 2 weeks within pituitary surgery.
• Prednisolone and hydrooctisone omitted 24 before
• OCP and HRT stopped 6 weeks prior

Question 6

What is the insulin intolerance test used for?

Answer 6

Performed to assess the pituitary function, adrenal function and insulin sensitivity.
- Gold standard for hypothalamus-adrenal axis

Question 7

What patient prep is needed for insulin tolerance test?

Answer 7

Patient must be hypoglycaemic before test (allow release of GH and ACTH)

• Cant be done in age>60, ischaemic heart disease, epilepsy, children <5
• Precaution ensuring patient has a normal ECG and serum cortisol>100nmol/L (9am)

Question 8

What is the protocol for insulin tolerance test?

Answer 8

1. Weigh the patient to determine insulin dose using 0.15U/kg for normal patients
2. Insert cannula
3. Take basal blood samples and inject insulin as i.v. bolus
4. Test cannot be interpreted unless hypoglycaemia has been achieved
   a. Glucose <2.2mmol/L (hypoglycaemic)
   b. Cortisol peak >430nmol/L
   c. GH peak > 6.7ug/L

Question 9

What is the glucagon stimulation test used for?

Answer 9

Assess the GH and cortisol reserve by stimulating its release through glucagon injection
- Indirectly stimulates cortisol secretion

Question 10

Who should not have a glucagon stimulation test?

Answer 10

inappropriate for patients with an adrenal insufficiency, hypothyroidism, starvation (>48hrs) or phaeochromocytoma/insulinoma.

Question 11

What is the protocol of glucagon ST?

Answer 11

1. Take basal sample for glucose, cortisol and GH
2. Give the glucagon IM
3. Start sample taking after 90min in 180min with 30min intervals

Question 12

What is the function of the growth hormone suppression test?

Answer 12

Assess GH secretion in response to glucose load. GH secretion should be inhibited. Test for acromegaly

Question 13

What patient prep is needed for growth hormone suppression test?

Answer 13

Fasting overnight 10-14hrs

Question 14

What is the protocol for growth hormone suppression test?

Answer 14

1. Take basal sample for GH, glucose and IGF1
2. Drink glucose solution within 5 min
3. Take sample every 30min for 120min

Normal response suppression of GH to <0.3ug/L

Question 15

What is the function of dexamethasone suppression test?

Answer 15

Screenin tool for cushings.
- assess adrenal gland function by measuring how cortisol levels change in response to oral doses or an injection of dexamethasone - ACTH should be suppressed in normal

Question 16

What is the protocol for dexamethasone suppression test?

Answer 16

1. take 1mg dexamethasone at 11pm
2. serum sample taken for cortisol at 9am

Physiological response: cortisol <50nmol/L

Question 17

What to investigate before an ITT?

Answer 17

Age
Heart disease - ECG
Ensure normal morning cortisol
Dont want them to be hypothyroidism