Thyroid Flashcards
Which test is performed to evaluate thyroid nodules for potential malignancy in a patient who has thyroid nodules and the primary care provider suspects thyroid cancer?
Radionuclide imaging
Serum TSH level
Serum calcitonin
Thyroid ultrasound
Thyroid ultrasound evaluation should be performed for all patients with known thyroid nodules; high-resolution sonography can clearly distinguish between solid and cystic components.
Testing for Thyroid Disorders
TSH testing is the most sensitive indicator. If TSH is abnormal, then test T3/T4
TSH Levels
TSH <0.3/0.5 = Hyerpthyroid
TSH 0.3 - 4.0 = Euthyroid
TSH > 4 = Hypothyroid
TSH levels increase in response to low T3/T4 and TSH level drops when T3/T4 is high.
TSH and T3/T4
High TSH with normal or slight low T3/T4 = subclinical hypothyroid
Low TSH and Low T3/T4 = Secondary hypothyroidism
Thyroid Antibody Test
Positive TBO = Hashimoto (autoimmune issues)
Thyroid Nodules
nodules are classified as hot, warm, or cold according to the concentration of iodine isotope in the nodule in comparison with the rest of the thyroid gland.
Hot nodules are usually but not always benign.
Most cold nodules (solid or cystic) are benign; however, most malignant neoplasms also appear as cold nodules
Thyroid Ultrasound / Scan
Always needed in hyperthyroid to rule out toxic nodules, does not assess thyroid function
Thyroid Cancer Signs / Risks
Exposure to radiation
Family history of thyroid cancer
Male gender
Older than 60
Thyroid Nodule Eval
Ultrasound
Fine Needle Aspiration
Nuclear scan if TSH is supressed
Hyperthyroid
TSH low, T3/T4 usually elevated
Graves Disease
Most common cause of hyperthyroid.
Autoimmune hyperhtyroid - autoantibodies actiavte thyroid hormone release
Hyperthyroid v. Thyroxicosis
Hyperthyroid - thyroid is source of excess thyroid hormone
Thyrotoxicosis - syndrome of excess thyroid hormone regardless of source (such as excess iodine)
Subacute thyroiditis
Postviral illness, tender thyroid
Hyperthyroid Presentation
High metabolism Tachycardia, palpitations, angina, hypertension Resltess, anxious Dry eyes, blurry vision Itching, menses irregularity Heat intolerance, high body temp Prominent goiter (Graves Disease)
Hyperthyroid Treatment
Beta blockers to relieve symptoms (prompranolol 10-40mg every 6 hours or atenolol 25mg daily)
Thioamide therapy - methimazole or PTU. PTU is not preferred for first line unless patient is first trimester pregnant or nursing
Thioamides have liver, arthlagia, and agranulocytosis risk
Radioiodine therapy is treatment of choice if thioamide therapy fails or severe cases
Thioamide Dosing
Methimazole - 5-20mg every 8 hours
PTU - 50-100 mg every 6/8 hours
Subclinical hyperthyroid
Low TSH, normal T3/T4
Treat if concerned for osteoporosis, Graves, risk for heart issues or heart comorbids, elderly
Subacute Thyroiditis
May need beta blockers for hyperthyroid phase
NSAIDs for pain relief or aspirin; prednisone if pain relief does not occur with those
Recheck thyroid levels every 2-8 weeks as hypothyroidism may follow
Thyroid Stom
rare, life-threatening form of hyperthyroidism that leads to systemic decompensation. The diagnosis is based on clinical findings: temperature of 102°F to 105°F, profuse sweating, pulse above 120 to 140 beats/min, atrial fibrillation, restlessness, confusion, agitation, and coma. Gastrointestinal symptoms may include severe vomiting, diarrhea, and hepatomegaly with jaundice
Refer to ED right away
Hypothyroidism
High TSH, low T3/T4
Hashimoto Thyroiditis
Autoimmune form of hypothyroid
Presence of antithyroid antibodies
Goiter may be present
Hypothyroid Presentation
Low metabolism effects Fatigue Cold intolerance Weight gain Puffiness of skin, hands Dry and brittle skin/hair Muscle aches Slow mentation
Subclinical Hypothyroid
Elevated TSH
Normal T4
Hypothyroid Treatment
Levothyroxine orally dosed to return TSH to normal
Usually 1.7 mcg/kg/day
Often start with 25-50 mcg per day (12.5 - 25 mcg for older adults)
Increase at 4-6 week intervals to get desired TSH level
MAX DOSE 100 MCG PER DAY
Hypothyroid Treatment Monitoring
Once desired TSH level achieved, monitor levels at least annually (every 6 months best)
If estrogen therapy is started or stopped, re-check TSH in 12 weeks
Subclinical Hypothyroid treatment
Usually treatment is not started unless TSH is above 10
Decision to treat depends on presence of secondary symptom severity
Type 1 diabetics may need treatment
Patients having depression / fatigue may need treatment
Myxedema Coma
Severe hypothyroid state
Respiratory depression, mental status changes
May be triggered by extreme stress, severe infection, substance that depresses CNS
Medical emergency, ED referral right away
Drugs that Affect Thyroid
Amiodarone - can cause hypothyroidism, even years after stopping the med
Lithium - can cause hypothyroid or thyroiditis
Biotin - May cause false low TSH levels or false elevates T3/T4 levels
Thyroid and Pregnancy
For hyperthyroid - PTU during first trimester, switch to methimazole after. Beta blockers to control symptoms until thiomaides work. Monitor fetal growth.
For Hypothyroid - Increase levothyroxine dose by 30% right away (can exceed 100mcg laily limit). Monitor thyroid levels, fetal growth. After delivery, return to pre-pregnancy doses and check levels in 6 weeks.
