Endocrine

Question 1

What are the causes of primary hypothyroidism?

Answer 1

Hashimoto thyroiditis
Iodine deficiency
Infiltrative diseases
Iatrogenic - thyroid sx, radioiodine therapy, neck irradiation

Question 2

How is hypothyroidism diagnosed?

Answer 2

TSH > 5.5 mIU/L -> measure serum free T4

High TSH and low serum free T4 = overt primary hypothyroidism

High TSH and normal serum free T4 = subclinical hypothyroidism

Low TSH or inappropriately normal TSH and a low serum free T4 level = secondary hypothyroidism and will usually be associated with further evidence of hypothalamic-pituitary insufficiency.

Question 3

Name the disorders associated with transient hypothyroidism.

Answer 3

Postpartum thyroiditis
Subacute thyroiditis
Silent thyroiditis
Thyroiditis associated with TSH receptor-blocking antibodies.

Question 4

Name some drugs associated with thyroid dysfunction.

Answer 4

Lithium
Amiodarone
Interferon alfa
Interleukin-2
Tyrosine kinase inhibitors

Question 5

What is starting dose of levothyroxine for older patients and patients with known or suspected ischemic heart disease?

Answer 5

25 - 50 mcg
(Inc. by 25 mcg q3-4 weeks)

Question 6

What are the most common symptoms of hypothyroidism?

Answer 6

Cold intolerance
Fatigue
Others: hair fall, weight gain, constipation, dry skin, depression, memory, concentration

Question 7

Does subclinical hypothyroidism need treatment?

Answer 7

Treat subclinical hypothyroidism if:
Serum TSH > 10 mIU/L
Patient desires pregnancy
Symptoms of hypothyroidism
Increased thyroid peroxidase antibody titre

Question 8

What is biologically active form of thyroid hormone?

Answer 8

T3
(T4 is produced in greater amounts)

Question 9

What is the starting dose of levothyroxine for patients younger than 50 that are not pregnant or have a TSH > or equal to 10 mIU/L?

Answer 9

1.6 mcg/kg/day

Question 10

What is the adjustment of levothyroxine in pregnancy?

Answer 10

Increase to 9 doses/week (one extra dose on 2 days of the week) and refer to endocrinology

Question 11

What medications should be avoided with levothyroxine?

Answer 11

Calcium and iron supplements should not be taken within four hours of taking levothyroxine

Question 12

What is the starting dose of levothyroxine in patients with subclinical hypothyroidism with serum TSH < 10 mIU/L?

Answer 12

50 mcg -> inc. by 25 mcg q6wks until TSH = 0.35 - 5.5

Question 13

What is Grave’s disease?

Answer 13

An autoimmune condition where TSH receptor antibodies cause primary hyperthyroidism. These TSH receptor antibodies, produced by the immune system, stimulate TSH receptors on the thyroid. This is the most common cause of hyperthyroidism.

Question 14

What is the 1st and 2nd line treatment for hyperthyroidism?

Answer 14

Carbimazole (1st line) - can cause acute pancreatitis
Propylthiouracil (2nd line) - can cause severe liver reactions
Both carry a risk of agranulocytosis

Question 15

What are the classic features of Cushing’s syndrome?

Answer 15

Moon facies
Buffalo hump
Central adiposity
Abdominal striae
Proximal limb wasting
Hirsutism
Easily bruising and poor skin healing

Question 16

What are the causes of Cushing’s syndrome?

Answer 16

C – Cushing’s disease (a pituitary adenoma releasing excessive ACTH)
A – Adrenal adenoma (an adrenal tumour secreting excess cortisol)
P – Paraneoplastic syndrome (ACTH released from a tumour somewhere other than pituitary - small cell lung carcinoma most common)
E – Exogenous steroids (patients taking long-term corticosteroids)

Question 17

Explain the dexamethasone suppression test.

Answer 17

For the low-dose overnight test, dexamethasone (1mg) is given at night (usually 10 or 11 pm), and the cortisol is checked at 9 am the following morning. A normal result is that the cortisol level is suppressed. Failure of the dexamethasone to suppress the morning cortisol could indicate Cushing’s syndrome, and further assessment is required.

Question 18

What is the test of choice for diagnosing adrenal insufficiency?

Answer 18

The short Synacthen test (ACTH Stimulation Test)
The test involves giving a dose of Synacthen, which is synthetic ACTH. The blood cortisol is checked before and 30 and 60 minutes after the dose. The cortisol level should at least double. A failure of cortisol to double indicates either:

Primary adrenal insufficiency (Addison’s disease)
Very significant adrenal atrophy after a prolonged absence of ACTH in secondary adrenal insufficiency

Question 19

Which medications block growth hormone release?

Answer 19

Bromocriptine (dopamine agonist)
Octreotide (somatostatin analogue)

Question 20

Name the primary causes of SIADH.

Answer 20

Postop
SSRI
Small cell lung carcinoma