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69 Cards in this Set

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Normal Lab Values: TSH
0.4 - 4.0 mU/L
Population mean TSH value.
1.2 mU/L.

This should be the target when titrating levothyroxine.
Normal Lab Values: Free T4
10 - 27 pmol/L
Clinical significance of total T4 levels.
Total T4 includes the free and protein bound T4 but it is NOT useful clinically. It is altered by the presence of exogenous estrogen, methodone, pregnancy, liver disease, etc.
Clinical significance of TSH levels.
Most reliable test of thyroid function. Used to diagnose all forms of hyper- and hypo thyroidism and to titrate thyroid replacement.
Clinical significance of free T4 levels.
After TSH, this is the most useful diagnostically.
Source of circulating T3.
20% is produced in the thyroid.
80% is converted peripherally from T4.
Clinical significance of Antiperoxidase Antibody.
Peroxidase is an enzyme found in thyroid cells. Presence of this enzyme indicates autoimmune thyroid disease.
Synonyms of Antiperoxidase Antibody.
Antimicrosomal antibody, thyroid peroxidase antibody (TPOAb), antithyroid antibody.
Hypothyroidism should be considered when a patient presents with this gynecological complaint:
New onset menorrhagia.
S/Sx of hypothyroidism: integumentary system.
Thick, dry skin.
Thick, coarse hair that breaks easily.
Thick, dry nails.
S/Sx of hypothyroidism: cardiac.
Bradycardia but only in severe cases.
S/Sx of hypothyroidism: GI.
Constipation.
S/Sx of hypothyroidism: reflexes.
Hyporeflexia.
"Hung up reflexes" where relaxation phase is slowed more than contraction phase.
S/Sx of hypothyroidism: GYN.
Menorrhagia.
S/Sx of hypothyroidism: weigh.
Slight weight gain of ~5 lb, mostly fluid.
S/Sx of hypothyroidism: mentation.
Lethargy, "thoughts too slow," can't make sense of things.
S/Sx of hypothyroidism: environmental sensitivity.
Cold intolerance.
S/Sx of hypothyroidism: musculoskeletal.
No change.
S/Sx of hyperthyroidism: integumentary system.
Smooth, silky skin that is sometimes moist.
Fine hair/loss of hair.
Thin, brittle nails.
S/Sx of hyperthyroidism: weight.
Loss of ~10 lb. Weight loss is present in ~50% of cases.
S/Sx of hyperthyroidism: cardiac.
Tachycardia, palpitations.
S/Sx of hyperthyroidism: reflexes.
Hyperreflexia.
S/Sx of hyperthyroidism: mentation.
Racing mind, "can't make sense."
S/Sx of hyperthyroidism: GI.
Frequent, low-volume, loose stool.
S/Sx of hyperthyroidism: GYN.
Oligomenorrhea.
S/Sx of hyperthyroidism: environmental response.
Heat intolerance.
S/Sx of hyperthyroidism: muscle strength.
Proximal muscle weakness.
Name 3 medications that may cause hypothyroidism.
Lithium, amiodarone, interferon.
Name two medications that may cause hyperthyroidism.
Amiodarone, interferon.
Presence of both hyper- and hypothyroidism suggests the patient is at increased risk for:
Other autoimmune conditions such as DM1, pernicious anemia, vitiligo, lupus, RA, Sjogren syndrome.
Population prevalence of thyroid disorders.
7%
Increased risk for thyroid conditions is present in these parts of the lifespan.
Elderly, postpartum.
Are thyroid conditions more prevalent in men or women?
Women.
This genetic condition is associated with increased risk for thyroid conditions.
Down syndrome.
This is the most helpful lab test to confirm an abnormal TSH.
Free T4.
Most common cause of hypothyroidism.
Hashimoto thyroiditis.
Expected immune titer findings in Hashimoto thyroiditis.
High levels of anti-TPO (peroxidase) and anti-thyroglobulin.
What is the most common cause of goiter in the US?
Hashimoto thyroiditis
Physical exam findings with Hashimoto thyroiditis.
Firm, diffusely enlarged thyroid with fine nodules.
Do patients with Hashimoto thyroiditis usually complain of pain?
No, but some neck fullness or tightness is sometimes noted.
Is T3 or T4 more metabolically active on body tissues?
T3.
Instructions for taking levothyroxine, and rationale.
Take first think in the morning with water ONLY. Wait at least 30 minutes before eating.

Levothyroxine is chelated by almost all metals (such as in antacids, iron, milk, etc.), which significantly alters absorption.
T/F: Levothyroxine requirements are usually stable once titrated.
True.
Define subclinical hypothyroidism.
Elevated TSH, normal T4, and no symptoms.
Indications for initiating levothyroxine in subclinical hypothyroidism.
When TSH > 10 mU/L, as this is often accompanied by significant increase in LDL.

Also consider starting when TSH >5 mU/L if antithyroid antibodies are present or the patient has a goiter.
Management principles for subclinical hypothyroidism:
If levothyroxine will not be initiated, watch and wait with TSH monitoring q 6 months.
Usual starting dose of levothyroxine:
For healthy adults: 1.6 mcg/kg/day, or about 75-125 mcg/day.

For elders: 1.0 mcg/kg/day or about 75% or adult dose.
Which of these is a bio-identical hormone:
a) levothyroxine
b) Armour Thyroid
c) Nature-Throid
d) Westhroid
a) Levothyroxine.

The others are dessicated thyroid preparations containing T3 and T4 from porcine thyroid.
How does pregnancy increase thyroid medication needs?
Levothyroxine needs increase by ~50% during pregnancy. Adjust dose upward by ~33% as soon as pregnancy is confirmed.
Considerations for initiating levothyroxine in the elderly:
Due to cardiovascular risk, the dose should be titrated slowly over 1-2 months. For example, start with 25% of predicted dose, then add 25% every 2 weeks. Then wait 6-8 weeks after reaching total dose before checking TSH.
At what interval should TSH be reassessed when titrating thyroid replacement therapy?
Every 6-8 weeks.
Levothyroxine is typically titrated by this amount:
12.5 - 25 mcg
Anticipatory guidance when starting young, healthy people on the entire anticipated levothyroxine dose.
They may feel jittery, shaky or nervous.
A patient who is taking levo 75 mcg daily has TSH = 4.5 mU/L on 8-week follow-up measurement. Next best action is to:
Increase by 25 mcg/day and reassess in 6-8 weeks. Although her TSH level is in the high end of normal, the target is 1.2 mU/L.
How often should TSH be monitored after thyroid replacement is titrated?
Every year or whenever pt is symptomatic.
What is the risk of malignancy of any thyroid nodule?
5%
What are some warning signs that suggest malignancy in thyroid masses?
Dysphonia, hemoptysis, regional lymphadenopathy, pain, dysphagia, and a fixed or hard mass.
On thyroid scan, malignant masses are usually hot or cold?
Cold.
Physical exam findings with Graves disease:
Diffuse, soft, enlarged thyroid. Exopthalmos, nervousness, tachycardia, and heat intolerance are also seen.
What is the most common form of hyperthyroidism?
Graves disease.
Initial management of Graves disease symptoms includes.
Start a non-selective beta-blocker (propanolol or nadolol) for tachycardia and tremor immediately, as antithyroid medications take some time to be effective.
First-line medical management of Grave's disease:
Antithyroid medications:
propylthiouracil (PTU)
methimazole (Tapazole)

These both inhibit thyroid hormone synthesis.
Second-line management of hyperthyroidism:
Radioactive iodine for thyroid ablation. This will cause lifelong hypothyroidism after treatment. Consult with endocrine is needed.
What is a major adverse effect of propylthiouracil and methimazole?
Liver toxicity.
What is an adverse effect of excessive levothyroxine use?
Bone thinning.
Name 3 drugs that may increase metabolism of levothyroxine:
Phenytoin
Rifampin
Phenobarbitol
Carbamazepine
What is the recommended diagnostic test to distinguish thyroid malignancy?
Fine Needle Biopsy
Which of these would appear as a "cold spot" on thyroid scan?
a) Graves disease
b) autonomously functioning adenoma
c) Hashimoto thyroiditis
d) thyroid cyst.
d) thyroid cyst