Hypothyroidism

Definition: High TSH + high, normal, or low free T4
Diagnosis
H&P is consistent with a diagnosis of hypothyroidism.
Labs: TSH, free T4, antithyroid antibodies (antithyroid peroxidase and antithyroglobulin), CBC, CMP, lipid panel, and CK.
Treatment
Levothyroxine 1.5 to 1.8 mcg/kg/day. Take in the AM, 1-2h prior to food. Missed pills may be taken during the day, 2-3hr after any calcium or iron supplements. If pt takes med QHS, it should be 4h after the last meal.
Elderly patients, pts with CAD, and pts at increased risk of ischemic heart disease: I start at 25-50mcg and titrate slowly.
Monitoring
Recheck TSH q6-8 weeks and adjust dose accordingly; Goal is TSH within the normal range. Once TSH is in range, we will recheck TSH q6-12mo.
-If TSH is in the normal range but the patient is still symptomatic, we will consider increasing the dose of levothyroxine with target TSH in the low normal range.
-Pt is advised to keep the same formulation of levothyroxine as recommended by AACE. If we must switch, will recheck TSH 6-8 weeks later.
-We will avoid tx interruptions by making sure the patient has refills. The patient was advised to inform me if a refill is needed or if anything happens that levothyroxine is needed.

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Important Hypothyroidism Pearls and Links

Thyroid disorders (both hypothyroidism and hyperthyroidism, including subclinical states) cause or worsen cardiovascular disease. Check and treat in patients at risk for CVD.
Central hypothyroidism.
Subclinical Hypothyroidism.
Major symptoms and signs of hypothyroidism.
Conditions that Require Higher Doses of Thyroid Medication (Levothyroxine).
Things that Impair Levothyroxine Absorption.
Anti-thyroid antibodies attack and destroy the thyroid gland leading to hypothyroidism. Two types are anti-tpo and antithyroglobulin.
**Positive antithyroid peroxidase (anti-TPO) and antithyroglobulin (anti-Tg) antibodies in > 90% of patients with Hashimoto’s thyroiditis.
May see hyponatremia, hypoglycemia, anemia, hyperlipidemia (increased LDL, low HDL), and elevated CK in Hashimoto’s thyroiditis.
TSH Receptor Antibodies (also called Thyroid Stimulating Antibodies) hyperstimulate the thyroid gland leading to hyperthyroidism (as seen in Graves disease, the most common cause of hyperthyroidism).

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