pre-IC14 & IC14 Flashcards
Compelling indications for screening of thyroid disorders
- Presence of autoimmune disease (eg. T1DM, cystic fibrosis)
- First-degree relative with autoimmune thyroid disease
- Psychiatric disorders
- Taking amiodarone or lithium
- Hx of head / neck radiation for malignancies
- Symptoms of hypothyroidism / hyperthyroidism
2 ways in which TH is regulated
- Negative feedback
- Peripheral conversion of T4 to T3
Which population is likely to have elevated TBG levels?
Pregnant woman or on estrogen
What happens when TBG levels are elevated?
FT3 & FT4 levels will go down because more of T3 & T4 will bind to the extra TBG
Antibody specific and confirmatory for Graves’ disease
TRAb: thyrotropin receptor IgG antibodies
Antibodies tested when Autoimmunity thyroid disorder is suspected
- ATgA: thyroglobulin antibodies;
- TPO: Thyroperoxidase antibodies (significantly a/w hypothyroidism)
- TRAb: thyrotropin receptor IgG antibodies
Who needs to undergo routine screening required for thyroid disease?
Pediatric patients and pregnant women
signs and symptoms of hyperthyroidism
- Weight loss or increased appetite
- Heat intolerance
- Goiter
- Fine hair
- Heart palpitations or tachycardia
- Nervousness, anxiety, insomnia
- Menstrual disturbances (lighter or more infrequent menstruation, amenorrhea)
- Sweating or warm, moist skin
- Exophthalmos in Graves disease
signs and symptoms of hypothyroidism
- Cold intolerance
- Dry skin
- Fatigue, lethargy, weakness
- Weight gain
- Bradycardia
- Slow reflexes
- Coarse skin and hair
- Periorbital swelling
- Menstrual disturbances (more frequent, more blood)
- Goiter
adverse effects for levothyroxine
- Cardiac abnormalities (tachyarrhythmias, angina, myocardial infarction)
- Risk of fractures
- Signs of hyperthyroidism
monitoring of therapy for levothyroxine
Monitor TSH (or FT4 if central hypothyroidism) and symptomatic relief every 2 months
antibodies positive for Hashimoto disease
ATgA and TPO antibodies
What scenarios could cause increased Creatine phosphokinase (CPK) levels?
Hypothyroidism/ statin use
Labs for primary hypothyroidism
- ↑TSH, ↓ T4
- Positive antibodies (TPO, ATgA)
Labs for central hypothyroidism
↓TSH, ↓ T4
Dosing for levothyroxine
- Young, healthy adults: 1.5 mcg/kg/d
- 50-60 years of age and no cardiac issues: 50 mcg daily
- With CVD: 25 mcg/d and titrate up
Titration for levothyroxine:
Can increase or decrease in _____ increments, or in ____ of weekly dose
12.5- to 25-mcg/day; 10%–15%
MOA for levothyroxine
Synthetic T4
endpoint for levothyroxine use
Treatment is lifelong but after a euthyroid state is achieved, thyroid function tests are recommended semiannually to annually in nonpregnant adult patients.
How to counsel levothyroxine with regards to administration timings?
Take at least 30 mins before bfast/4h aft dinner; Avoid milk/antacids/iron or calcium supplements at least 2h
MOA for Liothyronine
Synthetic T3
When to use liothyronine (T3)?
Myxedema Coma (as it is more potent)/ going for diagnostics e.g. CT scan (due to short half-life)
Dose incr for pregnant women with hypothyroidism
30-50% increase in pre- pregnant dosage to maintain euthyroid status
Target TSH in pregnancy & hypothyroidism
- 1st trimester: < 2.5 mIU/L
- 2nd trimester: < 3.0 mIU/L
- 3rd trimester: <3.5 mIU/L
What is subclinical hypothyroidism
Elevated TSH with normal T4
When to treat subclinical hypothyroidism
- TSH > 10 mIU/L (widely accepted)
- TSH 4.5–10 mIU/L and
I. Symptoms of hypothyroidism
II. TPO present
III. History of cardiovascular disease, heart failure, or risk factors for such
Treatment options for hyperthyroidism
- Surgical resection
- Radioactive iodine (RAI) ablative therapy
- Thyroidectomy (complete removal of thyroid gland)
- Antithyroid pharmacotherapy:
- Thionamides
- Iodides
- Non-selective beta-blockers
Absolute contraindication for Radioactive iodine (RAI) ablative therapy
Pregnancy
Examples of thionamides
Carbimazole & Propylthiouracil (PTU)
Adverse effects of thionamides
- Hepatotoxicity risk (boxed warning for PTU)
- Rash – risk for SJS
- Agranulocytosis early in therapy (usually within 3 months)
- Fever
MOA of thionamides
Inhibits iodination and synthesis of thyroid hormones;
PTU can additionally block T4/T3 conversion in the periphery at high doses
Thionamide: efficacy & monitoring
- Maximal effect may take 4–6
months - Monthly dosage titrations as needed (depending on symptoms and free T4 concentrations)
2 main symptoms in Hyperthyroidism & Pregnancy
- Failure to gain weight despite good appetite
- Tachycardia
Treatment for Hyperthyroidism & Pregnancy (for each trimester)
Treatment: Use lowest possible dose for thionamides; keep T4 at upper-normal limit
* 1st Trimester: Use PTU as Carbimazole have higher risk of congenital malformations
* 2nd and 3rd Trimesters: Use Carbimazole as PTU have higher risk of hepatotoxicity and yet less potent
Most commonly used NSBB for hyperthyroidism
Propranolol
MOA of NSBB for hyperthyroidism
Blocks many hyperthyroidism manifestations mediated by β- adrenergic receptors; also may block T4 conversion to T3 when used at high dose
MOA for iodides
Inhibits the release of stored THs. Minimal effect on hormone synthesis. Helps decrease vascularity and size of gland
What is Subclinical Hyperthyroidism
Low or undetectable TSH with normal T4
When to treat Subclinical Hyperthyroidism
More compelling if TSH < 0.10 mIU/L
Common drugs that induce hyperthyroidism
Amiodarone, lithium & IFN-alpha
