Thyroid Disease

Question 1

What are the serum thyroid markers?

Answer 1

TSH: Thyroid-Stimulating Hormone
T4: Thyroxine
T3: Triiodothyronine

Question 2

What is TSH/what does it do? How is it used in relation to diagnosing/monitoring thyroid disease?

Answer 2

TSH:
- produced by the anterior pituitary gland
- an endocrine MESSENGER
- most sensitive measure of thyroid disease ***

Question 3

What is T4 and what are the forms of it? Describe them.

Answer 3

T4 is made by the thyroid gland.

3 forms:
- Bound T4
- Free T4
- Total T4 = Bound T4 + Free T4

Bound T4:
- IS attached to proteins
- IS NOT effective because it’s too large to enter cells

Free T4:
- IS NOT attached to proteins
- IS effective because it can enter cells

Question 4

Describe T3 and its forms.

Answer 4

3 forms:
- Bound T3 is bound to proteins
- Free T3 is not bound to proteins
- Total T3 = Bound T3 + Free T3

Bound T3:
- about 99.5% of Total T3 circulates as Bound T3 &
- serves as a reserve

Total T3:
- is a more reliable measurement than Free T3

Question 5

What is the approximate ratio of T3 versus T4?

Answer 5

T3 is 5X more active than T4

Question 6

What diagnosis is marked by:
- elevated TSH
- low T4
- normal T3?

Answer 6

Primary hypothyroidism

Question 7

What condition would you diagnose for a patient with the following labs?

• elevated TSH
• normal T4
• normal T3

Answer 7

Subclinical hypothyroidism

Question 8

What diagnosis is appropriate for the following labs:
- low TSH
- elevated T4
- normal T3?

Answer 8

Primary hyperthyroidism

Question 9

How would you diagnose the following labs?

• low TSH
• elevated T4
• elevated T3

Answer 9

Primary hyperthyroidism

Question 10

What is the 2nd most common endocrine problem?

Answer 10

Primary hypothyroidism (95% of hypothyroid cases)

Question 11

What is a common cause of Primary Hypothyroidism?

Answer 11

Hashimoto’s thyroiditis

Question 12

Describe primary hypothyroidism.

Answer 12

• pathology lies in the thyroid gland
• reduction in the amount of circulating thyroid hormone (T3/T4)

Question 13

Describe secondary hypothyroidism.

Answer 13

• pathology is outside the thyroid gland
• RARE @ 5%

Question 14

Should subclinical hypothyroidism be treated? If so, in what cases?

Answer 14

Treatment of subclinical hypothyroidism is CONTROVERSIAL!

If TSH = 10+ mU/L:
- Treat to prevent progression to primary hypothyroidism

If TSH = 4.5 to <10:
- No benefit with treatment
- Monitor 6 - 12 months UNLESS patient becomes symptomatic/more symptomatic

Question 15

What medication is given to treat primary hypothyroidism and how should it be taken?

Answer 15

• L-thyroxine/Levothyroxine (synthetic T4)
• Given PO, in AM, on empty stomach (30 - 60 minutes before meal/other meds)

NOTE: Absorption on empty stomach varies 40% - 80% among patients

Question 16

Replacement levothyroxine for primary hypothyroidism should be based on what figure?

Answer 16

Patient’s ideal body weight

Question 17

What are the suggested initial levothyroxine doses for the following two groups of patients: young adults, middle adults (aged 50. - 60 years)?

Answer 17

Young adults: 1.6 mcg/kg/day

Middle adults: 50 mcg/day

Question 18

What is the suggested initial levothyroxine doses for the following group of patients: older adults or patients with underlying cardiac issues or multiple comorbidities? What is the rationale for initiating and adjusting doses for this group and why?

Answer 18

25 mcg/day

“Start low, go slow!”

The half-life of a levothyroxine tablet is 1 week. This group could have problems with delayed metabolism of the medication and toxic levels of the medication may accumulate if dosage increases are made too quickly.

Question 19

Following initiation of levothyroxine, how often and with what lab/s should patients be monitored?

Answer 19

• Recheck TSH every 4 - 6 weeks until euthyroid

THEN,

• Monitor TSH annually unless symptoms develop

Question 20

Describe hyperthyroidism and name the most common cause of it.

Answer 20

Body tissues are exposed to increased level of circulating thyroid hormone (T3 and/or T4)

Most common cause: Graves Disease

Question 21

How should hyperthyroid patients be handles in the primary care setting?

Answer 21

Hyperthyroidism should ALWAYS be referred to endocrinology!!!