NP Thyroid is a prescription thyroid medication made from dried, powdered pig thyroid glands. Manufactured for Acella Pharmaceuticals, it contains both of the thyroid hormones your body naturally produces: T4 (levothyroxine) and T3 (liothyronine). Each grain (60 mg) of NP Thyroid provides 38 mcg of T4 and 9 mcg of T3, in a roughly 4:1 ratio. It’s used to treat hypothyroidism, the condition where your thyroid gland doesn’t produce enough hormones on its own.
How NP Thyroid Differs From Synthetic Options
Most people with hypothyroidism take a synthetic version of T4 alone, such as levothyroxine. The body normally converts T4 into the more active T3 hormone as needed. Synthetic T4 medications contain only that one hormone and rely on your body to handle the conversion.
NP Thyroid takes a different approach. Because it’s derived from actual thyroid tissue, it delivers both T4 and T3 directly. Some patients and practitioners prefer this combination, particularly when people feel that T4-only medications leave them with lingering symptoms like fatigue, brain fog, or weight gain. The idea is that supplying both hormones more closely mimics what a healthy thyroid gland would release. That said, there is no validated conversion formula for switching between synthetic levothyroxine and desiccated thyroid products, which means dosing adjustments typically require careful lab monitoring.
How It Works in the Body
Once absorbed, the T3 and T4 from NP Thyroid work the same way your body’s own thyroid hormones do. T3 is the more potent of the two. It binds to thyroid hormone receptors inside your cells and activates genes that control your metabolic rate, essentially telling your body how fast to burn energy. T4 has similar effects but is weaker, and much of it gets converted into T3 in tissues like the liver and kidneys. Together, these hormones regulate everything from heart rate and body temperature to how quickly you digest food and how clearly you think.
Available Strengths
NP Thyroid comes in five tablet strengths, all tan-colored and debossed with “AP” on one side:
- 15 mg (1/4 grain), oval-shaped
- 30 mg (1/2 grain), round
- 60 mg (1 grain), round
- 90 mg (1 1/2 grain), round
- 120 mg (2 grain), round
The “grain” measurement is a holdover from traditional pharmacy. One grain equals 60 mg of thyroid extract. A 120 mg (2 grain) tablet, for example, contains 76 mcg of T4 and 18 mcg of T3, exactly double the single-grain dose. Dosing is highly individual and based on blood work, body weight, and symptom response.
FDA Regulatory Status
This is one of the more important things to understand about NP Thyroid. Despite being widely prescribed, it is technically an unapproved biological product. The FDA has stated clearly that no animal-derived thyroid product currently on the market has gone through its formal premarket evaluation process, which includes review of manufacturing controls, labeling, and supplier suitability.
Animal-derived thyroid products like NP Thyroid have been sold in the U.S. for decades, predating the modern drug approval system. Synthetic levothyroxine, by contrast, received FDA approval in 2002, and synthetic liothyronine was approved in 1956. The FDA now requires that animal-derived thyroid products obtain an approved biologics license application (BLA) to be legally marketed. As of a March 2020 regulatory change, these products can no longer be submitted through the older drug approval pathway. The FDA considers approved synthetic thyroid medications to be “safe and effective alternatives.”
This doesn’t mean NP Thyroid is dangerous or illegal to prescribe right now, but it does mean the product hasn’t been subjected to the same level of federal scrutiny as synthetic alternatives.
Recall History
NP Thyroid’s regulatory status became more than theoretical in April 2021, when Acella Pharmaceuticals issued a voluntary nationwide recall covering certain lots across all five tablet strengths. Routine testing found that the recalled lots were sub-potent, containing less than 90% of the labeled amount of T3 and/or T4. For someone relying on a precise dose of thyroid hormone every day, receiving a tablet that’s meaningfully weaker than expected can cause a return of hypothyroid symptoms: fatigue, weight changes, cold sensitivity, and mood shifts.
Potency consistency is a recognized challenge with animal-derived thyroid products more broadly. Because the raw material comes from biological tissue rather than chemical synthesis, there’s inherently more variability in the starting ingredient. This is one reason the FDA emphasizes the importance of the manufacturing controls that a formal approval process would evaluate.
Who Typically Uses NP Thyroid
NP Thyroid tends to appeal to patients who have tried synthetic T4 and still don’t feel well, or who prefer a medication derived from a natural source. Some practitioners in integrative and functional medicine prescribe it more frequently than conventional endocrinologists do. The combination of T4 and T3 in a single tablet is convenient compared to taking two separate synthetic prescriptions.
It’s worth noting, though, that the T4-to-T3 ratio in pig thyroid glands (roughly 4:1) is different from the ratio the human thyroid produces (closer to 14:1). This means NP Thyroid delivers proportionally more T3 relative to T4 than your own gland would. For some people, that extra T3 is exactly what helps them feel better. For others, it can push T3 levels higher than intended, particularly at higher doses. Regular blood tests are essential to make sure levels stay in range, especially when starting or adjusting the dose.