Cytomel vs. Synthroid for Thyroid Cancer and Hypothyroidism: Important Differences and Potential Risks.

Liothyronine

(Cytomel)

Synthroid

(levothyroxine)

Summary for Cytomel

Prescription only

Liothyronine (Cytomel) is a thyroid hormone medication that can be used for a number of thyroid-related health concerns. More specifically, it's a lab-made form of the T3 thyroid hormone that's made by your thyroid gland. People of all ages can take this medication, and it's generally taken by mouth just once daily. Although weight loss is a potential side effect of liothyronine (Cytomel), it should not be taken solely for this purpose.

Indications for Cytomel

Hypothyroidism (low thyroid hormone levels)
Thyroid cancer (with radiation and surgery)
Thyroid suppression test to help with diagnosis

Pros and Cons for Cytomel

Pros

Acts faster than other thyroid hormone replacement therapies
Safe to use during pregnancy
Safe to use in children
Available as a lower-cost generic version

Cons

Requires regular blood tests and frequent dose adjustments at first to make sure you're getting the right dose
Has a risk for heart problems
Can't use if you have untreated adrenal insufficiency
Shouldn't be used to treat conditions that aren't related to abnormal thyroid function (e.g., benign thyroid nodules, nontoxic goiter, swelling of the thyroid gland caused by infection)

Common Side Effects for Cytomel

Side effects are typically signs of having too much thyroid hormone in the body.

Shakiness
Fast or irregular heartbeat
Fever
Sweating
Easily feel hot
Hair loss
Larger appetite
Diarrhea
Weight loss
Weak muscles
Fatigue
Nervousness or anxiety
Irritability
Trouble sleeping
Trouble breathing

Warnings for Cytomel

Not for weight loss
Heart problems
Adrenal crisis in people with adrenal insufficiency
Worsening diabetes
Effect on bones if dose is too high

Summary for Synthroid

Prescription only

Synthroid (levothyroxine) is a thyroid hormone used to treat low thyroid hormone levels (hypothyroidism) in both children and adults. It's also used to treat a certain type of thyroid cancer. The medication comes as tablets in many different strengths. It's taken once a day by mouth, usually on an empty stomach in the morning. You'll need regular blood tests to make sure you're getting the right dose. Side effects can include headache, trouble sleeping, and weight loss.