Introduction
WP Thyroid is a natural desiccated thyroid (NDT) medication derived from porcine thyroid glands. It contains both thyroxine (T4) and triiodothyronine (T3) hormones in their natural ratio, along with other thyroid compounds naturally present in animal thyroid tissue. WP Thyroid is classified as a prescription thyroid hormone replacement therapy used to treat hypothyroidism.
Mechanism of Action
WP Thyroid works by replacing deficient endogenous thyroid hormones. The two primary active components are:
- Levothyroxine (T4): Converted peripherally to the more active T3
- Liothyronine (T3): Directly active at cellular level
These hormones enter cells and bind to nuclear receptors, regulating gene expression and influencing metabolic processes throughout the body, including:
- Basal metabolic rate
- Carbohydrate, protein, and lipid metabolism
- Growth and development
- Thermogenesis
- Cardiac function
- Neurological function
Indications
- Replacement therapy for hypothyroidism of any etiology
- Primary (thyroidal) hypothyroidism
- Secondary (pituitary) hypothyroidism
- Tertiary (hypothalamic) hypothyroidism
- Suppressive therapy for benign thyroid nodules and thyroid cancer (in some cases)
Dosage and Administration
Initial dosing: Typically 15-30 mg daily, adjusted in 15-30 mg increments every 2-3 weeks Maintenance dosing: Usually 30-120 mg daily Administration: Oral administration on an empty stomach, at least 30-60 minutes before breakfast Special populations:- Elderly patients: Start with 15 mg daily
- Cardiac patients: Start with 15 mg daily and titrate slowly
- Pediatric dosing: Based on body weight and age (consult pediatric dosing guidelines)
Pharmacokinetics
Absorption: Variable absorption (40-80%) from GI tract, significantly affected by food, calcium, iron, and other medications Distribution: Highly protein-bound (>99%) to thyroxine-binding globulin, prealbumin, and albumin Metabolism: Hepatic metabolism via deiodination, conjugation, and degradation Elimination: Renal excretion of conjugated metabolites; fecal elimination of unabsorbed hormone Half-life: T4: 6-7 days; T3: 1-2 daysContraindications
- Untreated subclinical or overt thyrotoxicosis
- Acute myocardial infarction
- Uncorrected adrenal insufficiency
- Hypersensitivity to any component of the formulation
- Untreated pituitary or hypothalamic disorders
Warnings and Precautions
- Cardiac effects: May exacerbate angina pectoris or precipitate arrhythmias in patients with cardiovascular disease
- Adrenal insufficiency: May precipitate adrenal crisis in patients with uncontrolled adrenal insufficiency
- Osteoporosis: Chronic overtreatment may accelerate bone loss and increase fracture risk
- Elderly patients: Increased risk of atrial fibrillation and other cardiac complications
- Pregnancy: Requires careful monitoring and dose adjustments
- Diabetes mellitus: May affect glycemic control and insulin requirements
Drug Interactions
Decreased absorption:- Calcium carbonate
- Iron supplements
- Aluminum-containing antacids
- Cholestyramine, colestipol
- Sucralfate
- Rifampin
- Carbamazepine
- Phenytoin
- Barbiturates
- Estrogens
- Androgens
- Salicylates
- Furosemide
- Amiodarone
- Lithium
- Interferon-alpha
- Tyrosine kinase inhibitors
Adverse Effects
Overtreatment (hyperthyroidism symptoms):- Palpitations, tachycardia
- Weight loss, increased appetite
- Heat intolerance, sweating
- Anxiety, nervousness, irritability
- Tremors, muscle weakness
- Insomnia
- Menstrual irregularities
- Fatigue, lethargy
- Weight gain, cold intolerance
- Constipation
- Dry skin, hair loss
- Depression
- Cognitive impairment
- Allergic reactions (rare)
- Temporary hair loss during initial months of treatment
- Pseudotumor cerebri (in children)
Monitoring Parameters
- Clinical assessment: Symptoms of hypo/hyperthyroidism, cardiac status
- TSH: Primary monitoring parameter (target 0.5-2.5 mIU/L for most patients)
- Free T4 and Free T3: Useful for assessing adequacy of replacement
- Vital signs: Heart rate, blood pressure, weight
- Bone density: Consider in patients on long-term therapy
- Lipid profile: Monitor improvement with adequate replacement
- Cardiac evaluation: ECG in patients with cardiac history or symptoms
Patient Education
- Take medication on an empty stomach, at least 30-60 minutes before breakfast
- Maintain consistent timing of administration daily
- Avoid taking with calcium, iron, or antacids (separate by at least 4 hours)
- Do not switch between different thyroid preparations without medical supervision
- Report symptoms of over- or under-treatment promptly
- Understand that dosage adjustments are common during initial treatment
- Regular follow-up and laboratory monitoring are essential
- Inform all healthcare providers about thyroid medication use
- Be aware that brand changes may require dose adjustments
References
1. Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism. Thyroid. 2014;24(12):1670-1751. 2. Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults. Endocr Pract. 2012;18(6):988-1028. 3. Wiersinga WM, Duntas L, Fadeyev V, et al. 2012 ETA Guidelines: The Use of L-T4 + L-T3 in the Treatment of Hypothyroidism. Eur Thyroid J. 2012;1(2):55-71. 4. FDA prescribing information for thyroid desiccated products 5. American Thyroid Association guidelines for thyroid hormone replacement 6. Peterson SJ, McAninch EA, Bianco AC. Is a Normal TSH Synonymous With "Euthyroidism" in Levothyroxine Monotherapy?. J Clin Endocrinol Metab. 2016;101(12):4964-4973. 7. Hennessey JV, Malabanan AO, Haugen BR, Levy EG. Adverse event reporting in treatment of hypothyroidism with levothyroxine in adults. Thyroid. 2016;26(11):1583-1589.