Levothyroxine: study card

Generic name

Levothyroxine

Class

Thyroid hormone (synthetic T4)

Mechanism

Synthetic T4; thyroid hormones enter the nucleus, bind thyroid receptor proteins on DNA and regulate gene transcription and protein synthesis.

Used for

Replacement therapy for congenital or acquired hypothyroidism; TSH suppression as an adjunct to surgery and radioiodine for thyrotropin-dependent, well-differentiated thyroid cancer

Common side effects

Palpitations from excessive thyroid-hormone replacement; Tachycardia from excessive thyroid-hormone replacement; Weight loss from excessive thyroid-hormone replacement; Heat intolerance from excessive thyroid-hormone replacement; Nervousness from excessive thyroid-hormone replacement

Boxed warning

Not for obesity or weight loss; larger doses may cause serious or life-threatening toxicity.

Warnings

Cardiac adverse reactions in elderly / CV disease; Uncorrected adrenal insufficiency; Worsening of diabetic control

Interactions

Calcium carbonate, ferrous sulfate; Bile acid sequestrants; PPIs, sucralfate, antacids

Brand questions use only name pairings verified against the linked product source. Unverified pairings are withheld from these questions; the other study content remains available.

Label date: 20260909 · For learning, not clinical decisions. US label and brand information; always consult the current source.

Source snapshot checked: 2026-10-21. The source document and selected fields were compared. The complete card has not had an independent clinical review.