Liothyronine is a synthetic form of triiodothyronine (T3), the active thyroid hormone, used primarily to treat hypothyroidism. Hypothyroidism is a condition where the thyroid gland does not produce enough hormone. Liothyronine works by supplying T3 to regulate metabolism and body function. Although the medication is intended to correct the hormonal imbalance that causes hair loss, Liothyronine itself is listed as having hair loss as a potential side effect. This article examines the relationship between Liothyronine use and hair health.
The Connection Between Thyroid Hormones and Hair Health
The hair growth cycle has three main phases: anagen (growth), catagen (transition), and telogen (rest and shedding). Thyroid hormones, specifically T3 and T4, play a direct role in regulating this cycle because hair follicles are highly sensitive to their levels. T3 and T4 stimulate hair matrix cell proliferation, which is necessary for the active anagen phase to occur.
When thyroid hormone levels are imbalanced, the hair growth cycle is disrupted, leading to increased shedding. Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) can prematurely push hairs into the telogen resting phase. This disruption results in diffuse hair thinning across the scalp, often noticed months after the imbalance began. Correcting the underlying thyroid issue is the first step to restoring healthy hair growth.
Liothyronine and Hair Loss: The Direct Connection
Liothyronine, as a replacement for the active thyroid hormone T3, has a known adverse event profile that includes hair loss. This drug-induced shedding is often linked to the short half-life of T3 compared to the commonly prescribed T4 medication, levothyroxine. If the Liothyronine dose is too high, it increases the body’s metabolic rate and can push the patient into a state resembling hyperthyroidism.
This state of over-treatment can disrupt the hair cycle, causing hair to shed in the same way natural hyperthyroidism does. The resulting hair loss is typically diffuse thinning. This recognized side effect does not affect every user and depends on the patient’s sensitivity and precise dosage. Adjusting the dose is often the solution if the hair loss is determined to be a direct consequence of excessive thyroid hormone levels.
Hypothyroidism Versus Treatment-Related Shedding
It is essential to distinguish between hair loss caused by the original disease and shedding that occurs during treatment. Hair loss due to untreated hypothyroidism is a slow, diffuse thinning caused by the lack of T3 and T4 shortening the hair’s active growth phase. When treatment with Liothyronine begins, a different phenomenon called Telogen Effluvium (TE) can occur.
Telogen Effluvium is a common type of diffuse shedding triggered by a physiological stressor, such as starting or adjusting thyroid medication. The body shifts from a stressed hypothyroid state to a normalized state, signaling a large number of telogen hairs to shed simultaneously. Patients typically notice this shedding two to four months after starting Liothyronine, often leading them to blame the medication. This shedding is generally temporary, lasting a few months as the hair cycle resets and the body adjusts to the corrected hormone levels.
Monitoring and Managing Hair Changes While on Liothyronine
If hair loss is noted while taking Liothyronine, the first step is to consult the prescribing physician for an evaluation. The medical team focuses on determining whether the cause is persistent hypothyroidism, medication-induced hyperthyroidism, or temporary Telogen Effluvium. This determination is made through blood tests, including Thyroid-Stimulating Hormone (TSH), Free T3, and Free T4 levels.
If blood work indicates over-treatment, the physician will likely reduce the Liothyronine dose to alleviate the hyperthyroid state triggering the hair loss. Alternatively, persistent shedding despite normalized thyroid levels may prompt a check for nutritional factors that can worsen hair loss, such as deficiencies in iron or zinc. Since Liothyronine dosing is individualized, careful monitoring and dose adjustments are necessary to find the optimal balance.