HRR Week 2 Flashcards
MOA for methimazole (Tapazole):
- Inhibits oxidative binding of iodide to thyroglobulin
- Inhibits coupling of iodide to tyrosine
Contraindications/cautions for methimazole (Tapazole):
Pregnancy, breastfeeding, hepatic impairment, agranulocytosis, myelosuppression
Serious side effects of levothyroxine (Synthroid):
CHF, arrythmias, HTN, angina
Common side effects of levothyroxine (Synthroid):
SSx of hyperthyroidism
MOA for propylthiouracil (PTU):
- Inhibits oxidative binding of iodide to thyroglobulin
- Inhibits coupling of iodide to tyrosine
- Inhibits peripheral conversion of T4 to T3
Contraindications/cautions for propylthiouracil (PTU):
Hepatic impairment, myelosuppression, peds
Indications for propylthiouracil (PTU):
Reserved for hyperthyroid patients who can’t take methimazole and who aren’t candidates for surgery or radioactive iodine tx
Contraindictions/cautions for liotrix (Thyrolar):
MI, adrenal insufficiency
Contraindications for levothyroxine (Synthroid):
Contraindications: MI, adrenal insufficiency, thyrotoxicosis, pre-existing TSH suppression.
Cautions: CV disease, elderly, DM
AEs for liotrix (Thyrolar):
Serious: arrythmias
Common: same as levothyroxine
Side effects for methimazole (Tapazole):
Most common: rash
Others: leukopenia, hypersensitivity, GI upset, transient elevated LFTs
Rare: Jaundice/hepatitis, agranulocytosis
Interactions with levothyroxine (Synthroid):
Beta blockers, bile acid sequestrants, carbamazepine and phenytoin, orlistat, OCPs, digoxine, theophylline, warfarin, amiodarone, phenobarbitol, rifampin, PPIs, sulcralfate
Patient education for levothyroxine (Synthroid):
- Take on empty stomach 30 - 60 min before breakfast, or at bedtime if it’s been 3 hours since last meal
- Don’t switch from brand to generic, or retest TSH in 6 weeks if you do
Patient education for methimazole (Tapazole):
May cause fetal harm if pregnant
Patient education for propylthiouracil (PTU):
May cause liver failure
T3 resin uptake:
- Old fashioned way of measuring free T3/T4 (not used anymore since free T3/T4 and TBG tests are available)
- Measures amount of TBG in the blood, which affects levels of free TT3/4
- Can help distinguish between true hyper/hypothyroidism and apparent hyper/hypothyroidism due to abnormal TBG
Causes of hypothyroidism:
- Hashimoto’s thyroiditis (most common)
- Iatrogenic (surgery, radiation)
- Drugs (amiodarone, lithium, iodine def.)
- Subacute/Postpartum thyroiditis
- Congenital
- 2-ary/central hypothyroidism (pituitary def.)
Definition of subclinical hypothyroidism:
Mildly elevated TSH, normal free T4
Guidelines for biopsy of thyroid nodules:
> 1 cm with high/intermediate suspicion
1.5 cm with low suspicion
2 cm with very low suspicion
What imaging technique should be used to evaluate suspected thyroid nodules?
Ultrasound
How is an I-123/I-131 scan used to evaluate thyroid nodules
- Done when TSH is suppressed
- In theory, “hot” nodules almost never cancerous
- Cold nodules should be biopsied (still, most cold nodules are benign)
Common etiologies of female and male hypergonadotropic hypogonadism:
- Female: Turner’s syndrome
- Male: Klinefelter syndrome
Name the gonadotropins:
- LH (leutenizing hormone)
- FSH (follicle stimulating hormone)
Describe the pathophysiology of hypergonadotropic vs hypogonadotropic hypogonadism:
- Hypergonadotropic: Source of the problem is at the gonads (ovaries or testes).
- Hypogonadotropic: Source of the problem is in pituitary or hypothalamus
- Gonadotropins (LH and FSH) are high, as well as GNRH since both of these systems are functional.
