Synthroid vs Prometrium: side-by-side comparison
Synthroid (Levothyroxine) and Prometrium (Progesterone) both belong to the Hormones and Birth Control class. They share clinical context but use different active ingredients. The choice between them depends on mechanism nuances, side-effect profile and individual response.
| Property | Synthroid | Prometrium |
|---|---|---|
| Active ingredient | Levothyroxine | Progesterone |
| Manufacturer | AbbVie | Catalent / Virtus |
| Class | Hormones and Birth Control | Hormones and Birth Control |
| Strengths | 25mcg, 50mcg, 75mcg, 100mcg, 150mcg | 100mg, 200mg |
| Forms | tablet | capsule |
What's the same
Synthroid and Prometrium both belong to the Hormones and Birth Control class and are used for partially overlapping indications. The active ingredients — Levothyroxine vs Progesterone — share the same therapeutic approach, so many safety and management points carry across both.
Key differences
Meaningful differences are in active ingredient (Levothyroxine vs Progesterone), strengths (25mcg, 50mcg, 75mcg, 100mcg, 150mcg vs 100mg, 200mg), forms (tablet vs capsule), and the mechanism, half-life and side-effect nuances that distinguish members of the class.
Mechanism and action
Synthroid: Levothyroxine replaces deficient endogenous thyroxine, which is converted in tissues to the active hormone triiodothyronine (T3) by deiodinase enzymes. Prometrium: Progesterone in Prometrium binds to progesterone receptors and modulates gene expression in reproductive and other tissues.
When Synthroid is preferred
Synthroid is approved for hypothyroidism of any cause (Hashimoto thyroiditis, post-thyroidectomy, post-radioiodine, congenital), goitre and TSH suppression after differentiated thyroid cancer.
When Prometrium is preferred
Prometrium is approved for endometrial protection in postmenopausal women receiving estrogen, secondary amenorrhoea and selected ART indications.
Frequently asked questions
Is Synthroid or Prometrium better? ▾
There is no single answer. Synthroid and Prometrium both belong to the Hormones and Birth Control class but differ in mechanism nuances, half-life and side-effect profile. Preference depends on the patient, the prescriber and prior response to other therapies.
Can I switch from Synthroid to Prometrium? ▾
Switching within the Hormones and Birth Control class is done under supervision, typically using equivalent doses and a follow-up period to confirm response and tolerance. It is not a self-directed decision.
Do Synthroid and Prometrium have the same side effects? ▾
They share many of the Hormones and Birth Control class side effects, with differences from mechanism and dose. Each medication's prescribing information lists specifics.
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The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.