The FDA informed manufacturers of its intent to issue draft guidance by August 2026 to regulate unapproved animal-derived thyroid medications used by 1.5 million Americans.
Earlier this month, the FDA announced a plan to issue new guidance for the regulation of unapproved and animal-derived thyroid medications, with intentions to issue the guidance to manufacturers by August 2026. According to a press release from the federal agency, it is actively applying a risk-based enforcement approach to unapproved, animal-derived medications.1
The FDA stated that millions of Americans take thyroid hormone replacement medications to treat hypothyroidism. The agency noted the importance of precise dosing, as too high or too low a dose “may not produce the intended effect, may increase the symptoms of hypothyroidism or may cause side effects,” requiring the monitoring of hormone levels closely.
The agency reported that animal-derived thyroid medications are not approved by the FDA. Still, an estimated 1.5 million patients received these prescriptions for outpatient retail and mail-order pharmacies in the United States.
“Due to their complex biological origin, these medications contain many compounds that are uncharacterized for safety and effectiveness,” wrote the FDA.
To increase compliance, the FDA points to the 2 types of thyroid hormone replacement medicines that are approved and currently available via prescription. According to the news release, the most common type of therapy is synthetic medications that contain levothyroxine or liothyronine. An estimated 22 million patients received prescriptions for levothyroxine dispensed by outpatient retail and mail-order pharmacies in 2024 in the United States.
“These medications have been FDA-approved for decades and are marketed as branded and generic medications containing levothyroxine sodium or liothyronine sodium,” the agency noted.
The agency informed manufacturers of the planned guidance on March 11, 2026, in addition to letting them know it intends to issue guidance in 2026 related to the development of these products to support the submission of marketing applications.
The FDA stated it could take action against manufacturers that are not meeting quality standards. The agency also noted that unapproved animal-derived medications for thyroid are not eligible for compounding because they are regulated as biological products under the Public Health Service Act.
The FDA posted the following concerns about unapproved medications, noting that these products do not face FDA review to ensure safety, purity, and potency. The FDA stated:
According to Johns Hopkins Medicine, the thyroid gland regulates metabolism and growth by producing thyroxine (T4), triiodothyronine (T3), and calcitonin. Thyroid disorders are significantly more common in those born female and can profoundly impact the reproductive system through hormone imbalances. Whether the gland is overactive (hyperthyroid) or underactive (hypothyroid), it can cause puberty to start at irregular times and lead to menstrual complications such as heavy bleeding or amenorrhea.2
These conditions also pose risks to fertility and bone health. An underactive thyroid increases the risk of ovarian cysts and may stop ovulation entirely, while an overactive thyroid can lead to osteoporosis due to calcium loss. Furthermore, thyroid issues are linked to early menopause—occurring before or in the early 40s—with symptoms like hot flashes and insomnia that often mimic menopausal transitions.
During pregnancy, thyroid dysfunction can lead to severe complications for both the birth parent and the fetus, including pre-eclampsia, preterm birth, and miscarriage. Beyond physical health, untreated disorders frequently impact emotional well-being, causing depressed mood, fatigue, and cognitive difficulties. Early identification and screening remain essential for managing these risks across all stages of life.
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