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HYPOTHYROIDISM

Initial Assessment (CPGH 2012)

  1. Only measure TSH in hospitalized patients if thyroid dysfunction suspected; in addition to measuring TSH:

    1. Obtain serum free T4 instead of total T4

    2. Do not measure total T3 or free T3

    3. In patients with central hypothyroidism, assess free T4 or free T4 index, not TSH, to diagnose and guide treatment

  2. Anti-thyroid antibody testing

    1. Consider anti-thyroid peroxidase antibody (TPOAb) in subclinical hypothyroidism

    2. Consider TPOAb to identify autoimmune thyroiditis when nodular thyroid disease is suspected to be autoimmune

  3. How to determine upper limit normal (ULN) for TSH

    1. Reference range changes with age; if an age-based ULN is not available in an iodine-sufficient area, use an ULN 4.12

  4. In patients with TSH levels above lab reference range

    1. Patients with serum TSH >10 have increased risk of heart failure and cardiovascular mortality; give thyroid replacement

    2. Patients with serum TSH between ULN and 10: Individualize treatment based on symptoms suggestive of hypothyroidism, positive TPOAb, or evidence of ASCVD or heart failure or risk factors for these

Acute Medical Management (CPGH 2012)

  1. Use L-thyroxine (T4) monotherapy

    1. Do not use combination T4 and T3 (L-triiodothyronine)

    2. Do not use dessiccated thyroid hormone

    3. Do not use TRIAC (tiratricol; 3,5,3-triiodothyroacetic acid) to treat primary or central hypothyroidism due to suggestion of harm

  2. Dosing L-thyroxine

    1. Patients resuming therapy after interruption less than 6 weeks and without intercurrent cardiac event or marked weight loss may resume their previous full replacement dose

    2. When initiating therapy in young healthy adults with overt hypothyroidism begin with full replacement doses

    3. When initiating therapy in patients older than 50–60 with overt hypothyroidism, without CAD, start 50 mcg daily

    4. In patients with subclinical hypothyroidism, start 25–75 mcg daily depending on the degree of TSH elevation

  3. Timing L-thyroxine therapy

    1. Take L-thyroxine with water 30–60 minutes before breakfast OR at bedtime 4 hours after the last meal

    2. Treat patients with combined adrenal insufficiency and hypothyroidism with glucocorticoids before starting L-thyroxine

  4. Who not to treat

    1. Do not treat with thyroid hormones empirically without lab confirmation

    2. Do not treat obesity with thyroid hormones if euthyroid

    3. Do not treat depression with thyroid hormones if euthyroid

  5. Consider endocrine consult if:

    1. Patients difficult to render and maintain euthyroid state

    2. Hypothyroid patients with cardiac disease

    3. Hypothyroid patients with goiter, nodule, or structural changes to gland

    4. Hypothyroid patients with other endocrine diseases, i.e., adrenal or pituitary

    5. Unusual constellation of thyroid test results

    6. Unusual causes of hypothyroidism, i.e., central or secondary causes

Management After Stabilization (CPGH 2012)

  1. Patients being treated with established hypothyroidism

    1. Measure TSH 4–8 weeks after initiating therapy or changing doses; once therapeutic, measure TSH at 6- and then 12-month intervals or when clinically indicated

    2. Remeasure TSH within 4–8 weeks of initiation of treatment with drugs that decrease the bioavailability or alter the metabolic distribution of L-thyroxine

    3. Consider checking serum free T4 with TSH

  2. Determining target TSH

    1. In nonpregnant patients, goal of therapy is a TSH ...

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