Endocrinology

Question 1

T4 Thyroid replacement

Answer 1

The average full replacement dose of T4 in adults is approximately 1.6 mcg/kg body weight per day.

• Re-evaluate measuring serum TSH in four to six weeks.
• If TSH is above the reference range, the dose of T4 can be increased by 12 to 25 mcg/day in older patients, or it can be increased by a higher dose in younger patients based on the degree to which the initial dose increased free T4 concentrations and reduced TSH concentrations.

-After identification of the proper maintenance dose, the patient should be examined and serum TSH measured once yearly or more often if there is an abnormal result or a change in the patient’s status.

• Dose needs to be increased during pregnancy, if weight gain, diminished absorption (malabsorption), increased thyroid hormone excretion (nephrotic syndrome), drug interactions (carbamazepine, phenytoin).

Medications that interfere with T4 absorption should be taken several hours after the T4 dose.

• If the TSH is slightly elevated (eg, 5 to 10 mU/L), a small increase of 12 to 25 mcg/day is usually sufficient.
• If the TSH is ≥10 mU/L, a larger dose increase (eg, 25 to 50 mcg/day) is usually necessary.

Because of the seven-day half-life of levothyroxine, another method of changing the dose without the need for a new prescription is to recommend increasing the dose by 15 percent by adding one tablet a week. For example, if a patient is taking 100 mcg/d (1 tablet a day), if they were to take 8 tablets a week (eg, 1 tablet a day for 6 days and 2 tablets on 1 day), this is equivalent to 114 mcg a day ([(100 x 8)/7 = 114]).

Question 2

A1C

Answer 2

5.7: prediabetes
6.5 or more: Diabetes, but requires 2 labs (A1C, random or fasting glucose)

In diabetics: A reasonable goal of therapy is an A1C value of ≤7.0 percent
- A1C goal should be set somewhat higher (eg, <8 percent [<64 mmol/mol]) for older patients and those with comorbidities or polypharmacy.
- A more stringent goal (A1C <6 percent [<42 mmol/mol]) is indicated during pregnancy.

Question 3

What measurement of thyroid nodule is an indication for FNA?

Answer 3

1cm or more, if nodule are solids or have suspicious features (microcalcifications or irregular margins)

Question 4

Indications for radionuclide uptake scan of thyroid?

Answer 4

• Nodule and low TSH (to look for a toxic nodule)

Question 5

U1 RNP antibody

Answer 5

AKA RNP antibody or nRNP)
Mixed connective tissue disease