Thyroid

Thyroid (desiccated thyroid) is used across several conditions affecting the thyroid gland. The tablet brands Amerithroid and Thyroid Tablets, USP are supported for the following uses:

• Hypothyroidism — replacement therapy when the thyroid gland doesn't produce enough hormone, from any cause (including surgery, radiation, or medications), in patients of any age including infants, children, adults, the elderly, and pregnant individuals
• Myxedema — a severe form of hypothyroidism, including myxedema coma (a medical emergency managed in hospital settings)
• Congenital hypothyroidism (cretinism) — treatment from infancy when a baby is born without adequate thyroid function
• Goiter prevention and treatment — TSH suppression to treat or prevent euthyroid goiters, thyroid nodules, and multinodular goiter
• Hashimoto's thyroiditis (chronic lymphocytic thyroiditis) — TSH suppression as part of management
• Thyroid cancer — used alongside radioactive iodine to suppress TSH as part of management of follicular and papillary thyroid carcinoma
• Thyroid suppression testing — used diagnostically to assess thyroid gland autonomy in certain patients

Desiccated thyroid supplies two naturally occurring thyroid hormones — levothyroxine (T4) and liothyronine (T3) — that the body needs to regulate metabolism. These hormones increase the rate at which the body uses oxygen and burns carbohydrates, fats, and proteins. They influence virtually every organ system, and are especially critical for normal brain and nervous system development. When the body receives thyroid hormone from an external source, the pituitary gland responds by producing less TSH — the hormone that normally stimulates the thyroid — which is why thyroid hormone can be used to shrink goiters or keep thyroid cancer in check.

About 80% of the active T3 in the body is actually made by converting T4 (the more abundant but less active hormone) into T3 in tissues like the liver and kidneys. Desiccated thyroid provides both hormones directly, which distinguishes it from synthetic levothyroxine-only products.

Thyroid tablets are taken by mouth, typically once daily. Dosing is always individualized — your prescriber starts at a low dose and adjusts gradually based on your lab results (T4, T3, and TSH levels) and how you feel. Fasting can improve absorption, so follow your prescriber's specific timing instructions. Missed-dose guidance should come from your prescriber or pharmacist — do not double up or adjust on your own.

• Amerithroid and Thyroid Tablets: started at a low dose, increased every 2–3 weeks as tolerated
• Children and infants require weight-based, age-adjusted dosing
• Patients with heart disease or severe long-standing hypothyroidism may need to start at an especially low dose
• Regular lab monitoring is essential — dose adjustments are typically reviewed within the first four weeks and ongoing

Most side effects from thyroid tablets are actually signs that the dose is too high — meaning the body is getting more thyroid hormone than it needs.

• Rapid or pounding heartbeat (palpitations)
• Chest pain or angina
• Nervousness, anxiety, or irritability
• Tremors (shakiness)
• Excessive sweating or feeling too warm
• Unintended weight loss
• Headache or difficulty sleeping

If you experience chest pain, a racing heart, or significant tremors, contact your prescriber promptly — your dose may need to be reduced. In a true overdose situation, seek emergency care immediately.

• Not for weight loss: Thyroid hormones must never be used to lose weight. In people with normal thyroid function, they don't cause meaningful weight loss — and high doses can be life-threatening, especially combined with stimulant diet drugs.
• Heart disease: Use with extreme caution if you have cardiovascular disease. Doses must be increased slowly and chest pain (angina) is a sign to reduce the dose immediately.
• Adrenal insufficiency: Thyroid hormone must not be started until untreated adrenal insufficiency is corrected — starting too soon can trigger an adrenal crisis.
• Porcine (pig) origin: The active ingredient in Thyroid Tablets, USP is derived from pig thyroid glands. No cases of disease transmission have been reported, but patients should be aware of this source.
• Not for infertility: Thyroid hormone is not appropriate for treating infertility unless hypothyroidism is confirmed as the cause.

Several medications and dietary factors can affect how thyroid hormone works or how much your body absorbs:

• Blood thinners (warfarin/oral anticoagulants): Thyroid hormones can amplify the blood-thinning effect — your anticoagulant dose may need to be lowered when starting thyroid therapy; close monitoring is essential
• Insulin and oral diabetes medications: Starting thyroid hormone can increase your requirements for insulin or diabetes pills — blood sugar should be monitored carefully
• Cholestyramine and colestipol (cholesterol-lowering resins): These drugs bind thyroid hormone in the gut and block its absorption — take thyroid hormone at least 4–5 hours before or after these medications
• Estrogens and estrogen-containing oral contraceptives: Estrogen raises levels of the protein that binds thyroid hormone in the blood, potentially reducing the amount of free (active) hormone — patients without a functioning thyroid may need a higher thyroid dose
• Dietary factors and soy formula (in children): Certain foods and soy-based infant formula can reduce absorption of thyroid hormone

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Do not take thyroid hormone if you have untreated adrenal cortical insufficiency — this must be treated first
• Do not take if you have untreated thyrotoxicosis (already too much thyroid hormone in your system)
• Tell your doctor if you have any heart disease, angina, or irregular heartbeat — dosing must be especially cautious
• Tell your doctor if you are pregnant — thyroid hormone is used in pregnancy but requires careful monitoring and dose adjustment
• Infants and children can be treated, but dosing is age- and weight-specific; follow prescriber guidance closely
• Tell your doctor if you have diabetes — your blood sugar medications may need adjustment
• Tell your doctor about all medications, especially blood thinners, cholesterol drugs, estrogen-containing products, and diabetes medications
• Note that the active ingredient is derived from porcine (pig) thyroid glands — discuss with your prescriber if this is relevant to you

Taking too much thyroid hormone creates a state similar to having an overactive thyroid — symptoms can include rapid heartbeat, fever, chest pain, agitation, tremors, and excessive sweating. If signs of overdose appear, the dose should be reduced or temporarily stopped and restarted at a lower level once symptoms resolve. Severe overdose requires emergency treatment focused on reducing further absorption, managing heart rate and symptoms, and supportive care — contact emergency services or poison control immediately.

Thyroid hormones boost the body's overall metabolic rate — essentially turning up how fast your cells use energy. They increase oxygen consumption across most tissues, speed up the breakdown of carbohydrates, fats, and proteins, and influence virtually every organ system. They are especially important for normal development of the central nervous system. When given in higher-than-replacement doses, they suppress the pituitary gland's release of TSH, which can reduce the size of goiters or help keep thyroid cancer from growing.

T4 (levothyroxine) is only partially absorbed from the gut — absorption can range from about 48% to 79% depending on what else is in the stomach, the intestinal environment, and other factors; fasting improves absorption. T3 (liothyronine) is much more completely absorbed — about 95% within 4 hours. Once in the bloodstream, more than 99% of both hormones bind tightly to proteins, with only a tiny free fraction being biologically active. T4 is converted to the more active T3 mainly in the liver, kidneys, and other tissues, with about 85% of T4 metabolized daily through this deiodination process. Some hormone is also processed through the bile and gut in what is called enterohepatic circulation.

Store in a tight container protected from light and moisture. Store between 15°C and 30°C (59°F and 86°F).