DS book objectives

Question 1

When is the best time to measure cortisol levels to assess ACTH deficiency?

Answer 1

Early morning: cortisol is diurnal, meaning it has a daily cycle. It rises early in the morning and drops during afternoon and evening.

Question 2

Why is cortisol measured for ACTH assessment?

Answer 2

ACTH has a short half life and measurements are rarely indicative of true physiologic levels. Cortisol is a more constant representation of ACTH levels.

Question 3

How do patients with primary Adrenal Insufficiency respond to CRH?

Answer 3

Primary adrenal insufficiency is a problem with the adrenal glands themselves. So a patient given CRH will have a spike in ACTH levels within 15 minutes because ACTH is released from the anterior pituitary. However, the cortisol levels will not rise because cortisol is released from the adrenal glands.

Secondary adrenal insufficiency is a problem with adrenal stimulation of cortisol release occurring somewhere in the pathway other than the adrenal glands (usually pituitary). If the pituitary is the problem, giving a patient CRH will cause no rise in ACTH levels or cortisol levels

Question 4

What is the best imaging modality for hypothalamus and pituitary images?

Answer 4

MRI: better resolution of normal vs abnormal tissue and defining tumors

Question 5

What is the most commonly secreted hormone from a pituitary adenoma?

Answer 5

Prolactin (PRL)

Question 6

What is the earliest manifestation of a pituitary adenoma in adults?

Answer 6

Endocrine dysfunction: hypogonadism

visual disturbances and MRI abnormalities don’t manifest until later because the gland needs time to hypertrophy

Question 7

What is the earliest manifestation of a pituitary adenoma in children?

Answer 7

Endocrine dysfunction: delayed puberty, diabetes Insipidus, low GH levels.

Question 8

Describe the main clause of empty sella syndrome?

Answer 8

Condition where the pituitary becomes atrophied or flattened due to increased pressure. Most common cause is herniation of the arachnoid and CSF into the sella.

Question 9

How successful is High Voltage Irradiation therapy for Cushing’s Disease and acromegaly?

Answer 9

Very successful at treating the condition (60-80%) show cessation of symptoms.

However, it should not be used because GH release is suppressed for up to 15 years resulting in long term endocrine defects.

Question 10

What are ACTH blood levels in:

1. normal adults
2. adrenal insuffiency
3. Cushing Syndrome
4. Congenital Adrenal Hyperplasia

Answer 10

1. 9-52 pictograms (pg)/mL
2. greater than 52pg/mL
3. less than 5pg/mL
4. greater than 52pg/mL

Question 11

Describe the Metyrapone Test and what are the expected levels of 11-deoxycortisol and ACTH.

Answer 11

Test to diagnose primary ACTH deficiency (pituitary)

In Normal People:

• Metyrapone inhibits the enzyme 11beta-hydrolyase which converts 11-deoxycortisol into cortisol
• the lack of cortisol stimulates release of ACTH from the pituitary
• the result is increased levels of 11-deoxycortisol and ACTH

Patients with primary ACTH deficiency have a problem with the ant. pit. and the ACTH levels won’t rise, only the 11-deoxycortisol levels will

Question 12

Describe the Rapid ACTH stimulation test

Answer 12

Assesses adrenal reserve and used to rule out primary adrenal insufficiency.

• 250ug of Cosyntropin (synthetic ACTH) are administered
• in a normal patient, cortisol levels will rise due to stimulation from the cosyntropin.
• in a patient that has an adrenal problem (primary adrenal insufficiency), cortisol levels will not rise

(important: this does not rule out SECONDARY adrenal insufficiency, only primary)

Question 13

Distinguish Cushing Syndrome from Cushing Disease

Answer 13

Syndrome: anything that causes a rise in glucocorticoid levels in the body

Disease: specific ACTH tumor in the pituitary that results in hypersecretion of glucocorticoids from the adrenal glands.

Cushing Disease actually causes Cushing syndrome, but Cushing syndrome does not have to be caused by Cushing Disease.

Question 14

What is ACTH dependent Cushing Syndrome vs. ACTH INdependent syndrome?

Answer 14

Dependent: some tissue (like a tumor) causes levels of ACTH to rise in the body. Examples include an ectopic ACTH tumor somewhere in the body or Cushing Disease (ACTH adenoma in the anterior pituitary)

Independent: there is no rise in ACTH. Some pathology within the adrenal gland causes high secretion of glucocorticoid secretion (like a tumor)

Question 15

Describe the overnight Dexamethasone Suppression Test.

Answer 15

Dexamethasone suppresses cortisol secretion.
Patients are given 1mg of Dexamethsone before bed and the cortisol levels are measured in the morning.

• In a normal person the cortisol levels will be suppressed
• In a person with Cushing Syndrome, the cortisol levels will not be suppressed.