Thyroid

The dosage of Thyroid USP must be individualized based on the patient's clinical response and laboratory findings (TSH, Free T4, and Free T3 levels).

• Standard Starting Dose: For otherwise healthy adults with mild hypothyroidism, a starting dose of 30 mg (1/2 grain) daily is common. This is typically increased by 15 mg increments every 2 to 3 weeks until the desired clinical effect is achieved.
• Maintenance Dose: Most adults require a maintenance dose of 60 mg to 120 mg (1 to 2 grains) per day. Doses exceeding 180 mg (3 grains) are rarely necessary and may indicate malabsorption or non-compliance.
• Myxedema Coma: Thyroid USP is NOT recommended for the emergency treatment of myxedema coma; intravenous synthetic T4 or T3 is the standard of care.

Thyroid USP can be used in children for congenital or acquired hypothyroidism. Dosing is highly sensitive to age and weight.

• Infants (0-6 months): 15 mg to 30 mg daily.
• Children (6-12 months): 30 mg to 45 mg daily.
• Children (1-5 years): 45 mg to 60 mg daily.
• Children (6-12 years): 60 mg to 90 mg daily.
• Adolescents: Dosing approaches adult levels (over 90 mg daily).

Healthcare providers monitor growth and bone age closely in pediatric patients to prevent over-replacement, which can lead to premature craniosynostosis (early fusion of skull bones) or accelerated bone maturation.

Renal Impairment

No specific dose adjustment is typically required for renal impairment, as the primary clearance of thyroid hormone is metabolic. However, patients with kidney disease should be monitored closely for electrolyte imbalances that might affect cardiac sensitivity to T3.

Hepatic Impairment

Since the liver is a major site of T4 to T3 conversion and hormone metabolism, patients with severe hepatic impairment may require more frequent laboratory monitoring and potential dose adjustments to maintain euthyroid status.

Elderly Patients

In patients over age 65, particularly those with underlying cardiovascular disease, the starting dose should be very low (e.g., 15 mg daily). The dose should be increased very slowly (every 6 to 8 weeks) to avoid precipitating cardiac events like angina or arrhythmias.

• Timing: Thyroid USP should be taken once daily on an empty stomach, ideally 30 to 60 minutes before breakfast.
• Consistency: Take the medication at the same time every day to maintain stable hormone levels.
• Absorption Barriers: Do not take Thyroid within 4 hours of taking calcium supplements, iron supplements, antacids (containing aluminum or magnesium), or bile acid sequestrants (like cholestyramine), as these significantly inhibit absorption.
• Storage: Store at room temperature (68°F to 77°F) in a tight, light-resistant container. Keep away from excessive moisture.

If you miss a dose, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and return to your regular schedule. Do not double the dose to catch up. Frequent missed doses will result in a return of hypothyroid symptoms.

Signs of acute Thyroid USP overdose (thyrotoxicosis) include palpitations, rapid heart rate, tremors, heat intolerance, excessive sweating, insomnia, and confusion. In severe cases, it can lead to cardiac failure or "thyroid storm." If an overdose is suspected, contact a Poison Control Center or seek emergency medical care immediately. Treatment usually involves supportive care and beta-blockers to manage cardiac symptoms.

> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or switch brands without medical guidance, as different brands of Thyroid USP may have slight variations in hormone content.

Side effects of Thyroid USP are almost exclusively related to therapeutic over-replacement (hyperthyroidism). When the dose is appropriate, side effects are rare. Common symptoms of excessive dosage include:

• Tachycardia: A fast or racing heartbeat that may be felt in the chest.
• Anxiety and Nervousness: Feeling "on edge," jittery, or unusually irritable.
• Insomnia: Difficulty falling asleep or staying asleep due to increased metabolic stimulation.
• Weight Loss: Unintentional weight loss despite a normal or increased appetite.
• Heat Intolerance: Feeling excessively warm when others are comfortable, often accompanied by increased sweating (diaphoresis).

• Tremors: Especially noticeable in the hands.
• Diarrhea: Increased frequency of bowel movements or loose stools.
• Muscle Weakness: Particularly in the proximal muscles (shoulders and hips).
• Menstrual Irregularities: Changes in the timing or flow of menstrual periods.
• Increased Appetite: A significant increase in hunger.

• Alopecia: Temporary hair loss may occur during the first few months of therapy, particularly in children. This usually resolves as the body adjusts.
• Pseudotumor Cerebri: Benign intracranial hypertension has been rarely reported in children receiving thyroid replacement.
• Hypersensitivity Reactions: Since the product is porcine-derived, rare allergic reactions to pig proteins can occur, manifesting as rash, hives, or itching.

> Warning: Stop taking Thyroid and call your doctor immediately if you experience any of these serious cardiovascular or neurological symptoms:

• Chest Pain (Angina): This may indicate that the heart is being overworked by the increased metabolic demand.
• Shortness of Breath: Especially when lying down or during mild exertion.
• Fainting or Dizziness: May indicate an underlying arrhythmia (irregular heartbeat).
• Seizures: Extremely rare but possible in cases of severe thyrotoxicosis.
• Rapid/Irregular Pulse: Feeling like your heart is skipping beats or fluttering.

• Bone Mineral Density Loss: Chronic over-replacement with thyroid hormone (suppressed TSH) is a known risk factor for accelerated bone turnover, which can lead to osteoporosis and an increased risk of fractures, particularly in postmenopausal women.
• Cardiac Hypertrophy: Long-term subclinical hyperthyroidism can lead to structural changes in the heart and an increased risk of atrial fibrillation.

FDA BLACK BOX WARNING: NOT FOR WEIGHT LOSS

Thyroid hormones, including Thyroid USP, should not be used for the treatment of obesity or for weight loss. In euthyroid patients (those with normal thyroid function), doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic (appetite suppressant) effects. Using thyroid medication for weight loss is a dangerous misuse of the drug.

Report any unusual symptoms to your healthcare provider. Regular blood tests are required to ensure your dose remains in the safe and effective range.

Thyroid USP is a potent hormone. It should only be used by patients with a confirmed diagnosis of thyroid deficiency or specific goiter conditions. It is not a general "energy booster" or "metabolism pill." Patients with underlying heart disease must use extreme caution, as thyroid hormones increase the heart's workload and oxygen demand.

As noted in the side effects section, Thyroid USP carries a strict FDA Black Box Warning against its use for weight loss. Misuse of this medication for obesity can lead to cardiac arrest, stroke, and death, especially if combined with diet pills.

• Cardiovascular Disorders: Thyroid hormone should be used with great caution in patients with cardiovascular disorders, including angina, coronary artery disease, and hypertension. If chest pain or worsening of cardiovascular symptoms occurs, the dose must be reduced.
• Adrenal Insufficiency: Patients with concomitant adrenal insufficiency (an underactive adrenal gland) must be treated with glucocorticoids (like hydrocortisone) before starting Thyroid USP. Starting thyroid hormone first can trigger an acute adrenal crisis, which is a life-threatening medical emergency.
• Diabetes Mellitus: Thyroid hormone replacement may increase blood glucose levels. Patients with diabetes may require an adjustment (increase) in their insulin or oral hypoglycemic medications once thyroid therapy begins.
• Myxedema: Patients with severe, long-standing hypothyroidism (myxedema) are highly sensitive to thyroid hormones. Dosing must start extremely low to avoid cardiac collapse.

To ensure safety and efficacy, the following monitoring is required:

• TSH (Thyroid Stimulating Hormone): The primary marker for dose adjustment. In primary hypothyroidism, the goal is typically to keep TSH within the normal reference range (0.5 to 4.5 mIU/L).
• Free T4 and Free T3: These levels are often checked alongside TSH, especially when using Thyroid USP, to ensure T3 levels do not become supra-therapeutic (too high).
• Clinical Assessment: Regular monitoring of heart rate, blood pressure, and weight.
• Bone Density: Periodic DEXA scans may be recommended for patients on long-term TSH-suppressive therapy.

Thyroid USP generally does not affect the ability to drive or operate machinery. However, if a patient experiences tremors, nervousness, or dizziness due to over-replacement, they should avoid these activities until their levels are stabilized.

There is no direct contraindication between alcohol and Thyroid USP. However, alcohol can exacerbate some of the side effects of hyperthyroidism, such as rapid heart rate and sleep disturbances. Moderate use is generally considered safe, but patients should discuss their habits with their doctor.

Thyroid hormone replacement is usually a lifelong therapy. You should never stop taking Thyroid USP suddenly unless directed by a physician. Discontinuing the medication will result in the return of hypothyroid symptoms (fatigue, weight gain, depression, cold intolerance) within days to weeks as the hormone levels fall.

> Important: Discuss all your medical conditions, especially heart problems or adrenal issues, with your healthcare provider before starting Thyroid.

There are few absolute contraindications for drug combinations, but Thyroid USP should never be used with high-dose sympathomimetic amines (diet pills or certain stimulants) for the purpose of weight loss, as this increases the risk of fatal cardiac arrhythmias.

• Oral Anticoagulants (e.g., Warfarin): Thyroid hormones increase the catabolism (breakdown) of vitamin K-dependent clotting factors. When starting Thyroid USP, the effect of warfarin is intensified, significantly increasing the risk of bleeding. Prothrombin time (PT/INR) must be monitored closely, and the warfarin dose usually needs to be decreased.
• Insulin and Oral Antidiabetics: As thyroid function improves, the body's clearance of insulin and the metabolic handling of glucose change. Patients often require more insulin or diabetes medication as they move from a hypothyroid to a euthyroid state.
• Digitalis Glycosides (e.g., Digoxin): Hypothyroidism reduces the clearance of digoxin. As Thyroid USP restores normal metabolism, the renal clearance of digoxin increases, potentially requiring an increase in the digoxin dose to maintain therapeutic levels.

• Ketamine: Use in patients on thyroid hormone may lead to marked hypertension and tachycardia.
• Theophylline: The clearance of theophylline is decreased in hypothyroid patients and returns to normal when the euthyroid state is restored.
• Tricyclic Antidepressants: Concurrent use may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity.

• Soybean Flour/Soy Products: Known to decrease the absorption of thyroid hormones. Patients who consume large amounts of soy may require higher doses of Thyroid USP.
• High-Fiber Diets: Excessive dietary fiber can bind to thyroid hormones in the gut, reducing absorption.
• Grapefruit Juice: May slightly delay the absorption of T4, though the clinical significance is usually minimal compared to other interactions.
• Walnuts and Cottonseed Meal: These have also been shown to reduce thyroid hormone absorption.

• Calcium Carbonate: A very common interaction. Calcium binds thyroid hormone in the GI tract. Must be separated by at least 4 hours.
• Ferrous Sulfate (Iron): Similar to calcium, iron supplements significantly impair the absorption of Thyroid USP.
• Biotin (Vitamin B7): Biotin does not interact with the medication itself, but it interferes with thyroid lab tests. It can cause falsely high T3/T4 and falsely low TSH results. Stop biotin 3-5 days before blood work.

Thyroid USP can alter the results of various tests:

• Protein-Bound Iodine (PBI): Will be increased.
• Blood Glucose: May be elevated in diabetic patients.
• Lipid Profile: Cholesterol and triglyceride levels typically decrease as the patient becomes euthyroid.

For each major interaction, the management strategy is typically to separate dosing by 4 hours (for absorption issues) or to perform frequent lab monitoring (for systemic drug interactions).

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, including over-the-counter vitamins.

Thyroid USP must NEVER be used in the following circumstances:

• Untreated Adrenal Insufficiency: Thyroid hormone increases the metabolic clearance of glucocorticoids. In a patient with adrenal insufficiency, starting thyroid hormone can precipitate an acute adrenal crisis (symptoms include shock, extreme low blood pressure, and death).
• Uncorrected Thyrotoxicosis: Giving additional thyroid hormone to a patient who already has excess thyroid hormone (hyperthyroidism) is dangerous and can lead to thyroid storm.
• Acute Myocardial Infarction (Heart Attack): In the acute phase of a heart attack, the heart is fragile. Increasing metabolic demand and heart rate with thyroid hormone can worsen cardiac damage or cause fatal arrhythmias.
• Hypersensitivity to Porcine Products: Since Thyroid USP is derived from pigs, patients with a documented, severe allergy to pork or porcine-derived products should not use this medication.

Conditions requiring a careful risk-benefit analysis include:

• Angina Pectoris: The risk of worsening chest pain must be weighed against the need for hormone replacement.
• Severe Hypertension: Blood pressure must be stabilized, as thyroid hormone can further increase heart rate and pressure.
• Osteoporosis: In patients with low bone density, TSH must be monitored very strictly to avoid even mild over-replacement, which accelerates bone loss.

There is no known cross-sensitivity between synthetic levothyroxine and Thyroid USP. Patients who are allergic to the dyes or fillers in synthetic tablets may often tolerate Thyroid USP, and vice versa. However, the pig-protein component is unique to desiccated products.

> Important: Your healthcare provider will evaluate your complete medical history, including any history of heart disease or allergies, before prescribing Thyroid.

FDA Pregnancy Category A.

Thyroid hormones do not readily cross the placental barrier in significant amounts. However, maintaining normal thyroid levels is critical for both the mother and the developing fetus. Untreated hypothyroidism during pregnancy is associated with a higher rate of miscarriage, pre-eclampsia, and stillbirth, as well as impaired neurological development in the child.

• Dose Requirements: Thyroid requirements often increase during pregnancy (frequently by 30-50%). TSH should be monitored every 4 weeks during the first half of pregnancy.
• Postpartum: Doses usually return to pre-pregnancy levels immediately after delivery.

Small amounts of thyroid hormones are excreted in human milk. However, when the mother is taking a proper replacement dose, this is not associated with adverse effects in the nursing infant. Thyroid USP is generally considered compatible with breastfeeding. It does not interfere with milk production.

Thyroid USP is used for congenital hypothyroidism (cretinism) and acquired hypothyroidism in children.

• Urgency: In infants, restoring thyroid levels within the first few weeks of life is essential to prevent permanent intellectual disability and stunted growth.
• Monitoring: Pediatricians monitor height, weight, and bone age. Over-treatment can cause the bones to mature too quickly, potentially leading to shorter adult stature.

Patients over age 65 are more sensitive to the cardiac effects of T3 (triiodothyronine).

• Start Low: Clinical guidelines suggest starting at 15 mg daily.
• Polypharmacy: Elderly patients are more likely to be on medications that interact with Thyroid USP, such as blood thinners or heart medications.
• Atrial Fibrillation: There is an increased risk of developing atrial fibrillation if the TSH becomes suppressed in this age group.

No primary dose adjustment is needed for patients with reduced GFR. However, kidney disease can affect the binding proteins (like albumin) that carry thyroid hormone in the blood. Lab results should be interpreted with caution in patients with nephrotic syndrome.

In patients with cirrhosis or severe liver disease, the conversion of T4 to T3 may be impaired. These patients may require a product containing T3 (like Thyroid USP) more than a T4-only product, but they must be monitored closely for signs of toxicity since the liver also clears these hormones.

> Important: Special populations require individualized medical assessment and more frequent blood testing.

Thyroid USP provides an exogenous source of the hormones T4 and T3. The primary molecular mechanism involves the entry of T3 into the cell nucleus, where it binds to thyroid hormone receptors (TRs). These receptors are associated with "thyroid response elements" (TREs) on the DNA. Binding triggers the recruitment of co-activators and the release of co-repressors, leading to the transcription of specific messenger RNA (mRNA). This process results in the synthesis of new proteins that increase mitochondrial activity, sodium-potassium ATPase activity, and overall cellular metabolism.

• Onset of Action: T3 acts rapidly, with effects often felt within 24 to 48 hours. T4 acts more slowly, as it must be converted to T3, taking several days to reach peak effect.
• Duration: After a single dose, the effects can last for several days due to the long half-life of the T4 component.
• Tolerance: Physiological tolerance does not develop; however, the body's requirement for the hormone may change over time due to age, weight changes, or disease progression.

| Parameter | Value (T4 / T3) |

|---|---|

| Bioavailability | 40-80% (T4) / 95% (T3) |

| Protein Binding | 99% (Both) |

| Half-life | 6-7 days (T4) / 1-2 days (T3) |

| Tmax | 2-4 hours (T4) / 1-2 hours (T3) |

| Metabolism | Deiodination in Liver/Kidney |

| Excretion | Renal (primarily), Fecal |

Thyroid USP is a natural substance. Its primary active components are:

• Levothyroxine (T4): C15H11I4NO4; Molecular Weight: 776.87 g/mol.
• Liothyronine (T3): C15H12I3NO4; Molecular Weight: 650.97 g/mol.

It is a yellowish-tan powder with a characteristic odor, derived from the cleaned, dried, and powdered thyroid gland of Sus scrofa (pig).

Thyroid USP is categorized as a Thyroid Preparation or Thyroid Hormone Replacement. It is distinct from synthetic levothyroxine (T4 only) and synthetic liothyronine (T3 only) because it is a combination product of natural origin.