Thyroid extract (Desiccated thyroid) is a thyroid replacement therapy that is prepared from the animal thyroid gland. It is obsolete in most parts of the world. It contains both levothyroxine (T4) and tri-iodothyronine (T3). It was used to treat patients with hypothyroidism.

Thyroid extract Uses:

• Hypothyroidism:

  • Used for replacement or supplemental therapy in patients with hypothyroidism

Thyroid extract dose in Adults

Note: The American Thyroid Association/American Association of Clinical Endocrinologists has not recommended using desiccated thyroid as replacement therapy for hypothyroidism. Tablet strengths may vary by manufacturer in terms of grains or mg; dosing recommendations are based on general clinical equivalencies that 1 grain = 60 mg or 65 mg; 1/2 grain = 30 mg or 32.5 mg; and 1/4 grain = 15 mg or 16.25 mg.

Thyroid extract dose in the treatment of Hypothyroidism:

• Oral: Initial: 30 or 32.5 mg per 24 hours; dose may be increased in 15 or 16.25 mg increments every 2 to 3 weeks until adequate replacement dose determined; start with 15 or 16.25 mg/day in patients with cardiovascular disease or long-standing myxedema.
• The usual dosage range: 60 to 130 mg per 24 hours.
• Inadequate response to doses up to 195 mg per 24 hours can be due to noncompliance or malabsorption.

Thyroid extract dose in children:

Note: Doses presented as mg/kg/dose or mg/dose; closely review dosing units; dose should be adjusted based upon clinical response and laboratory parameters. Tablet strengths may vary by manufacturer in terms of grains or mg; dosing recommendations are based on general clinical equivalencies that

• 1 grain = 60 mg or 65 mg;
• 1/2 grain = 30 mg or 32.5 mg; and
• 1/4 grain = 15 mg or 16.25 mg.

Thyroid Extract Dose in the treatment of Congenital hypothyroidism:

Note: Desiccated thyroid use over levothyroxine monotherapy is not recommended by the guidelines for the management of hypothyroidism. Start therapy at full dose in infants  Oral:

• Infants 1 to 6 months:

  • 8 to 6 mg/kg/dose or 15 to 32.5 mg/dose once a day

• Infants >6 to 12 months:

  • 6 to 4.8 mg/kg/dose or 30 to 48.75 mg/dose once a day

• Children 1 to 5 years:

  • 3 to 3.6 mg/kg/dose or 45 to 65 mg/dose once a day

• Children 6 to 12 years:

  • 4 to 3 mg/kg/dose or 60 to 97.5 mg/dose once a day

• Adolescents:

  • Typical doses 1.2 to 1.8 mg/kg/dose or >90 mg/dose once a day

Pregnancy Risk Factor A

• The placenta only contains a small amount of endogenous thyroid hormones.
• The use of desiccated thyroid during pregnancy by mothers has not been shown to have an adverse effect on the fetus.
• Uncontrolled maternal hypothyroidism can lead to adverse maternal and neonatal outcomes.
• Mothers with low serum thyroxine levels at the beginning of their first trimester may experience subnormal intellectual development. 
• To avoid adverse events, maintain normal thyroid function in the mother during pregnancy.
• Desiccated thyroid should not be used during pregnancy as it can cause serum thyroxine levels to drop.
• Switch to a preferred treatment for women who have desiccated thyroid and are pregnant or planning to conceive.
• Monitor the TSH.

Thyroid extract use during breastfeeding:

• Breast milk does not contain any endogenous thyroid hormones and has no adverse effects.
• Breastfeeding women should exercise caution if desiccated thyroid medication is given.

Dose in Kidney Disease:

No dosage adjustments provided in the manufacturer's labeling.

Dose in Liver disease:

No dosage adjustments provided in the manufacturer's labeling.

Side effects of thyroid extract:

Adverse reactions indicate excess thyroid replacement and/or hyperthyroidism.

Contraindications to Thyroid extract:

• Hypersensitivity to any component of the formulation
• Thyrotoxicosis untreated
• Uncorrected adrenal insufficiency

Warnings and precautions

• Insufficiency of the adrenal glands:

  • You should be cautious with adrenal insufficiency.
  • Therapy may cause exaggeration and aggravation of symptoms. Uncorrected adrenalinsufficiency can be dangerous.
  • Patients with adrenal insufficiency should receive glucocorticoid therapy before receiving thyroid replacement therapy.

• Cardiovascular disease

  • Patients with angina pectoris and other cardiovascular conditions should exercise caution. May require dose reduction.
  • Hypothyroidism can lead to coronary artery disease.

• Diabetes:

  • Diabetes mellitus or diabetes insipidus can be dangerous. Therapy may lead to the exacerbation of symptoms.

• Myxedema

  • Myxedema can be exaggerated and aggravated by therapy.
  • Patients with persistent myxedema should reduce their dosage immediately.

Thyroid extract (desiccated thyroid): Drug Interaction

Monitoring parameters:

• Monitor TSH 4 to 6 weeks after starting a treatment or dose changes, then 4 to 6 months after adequate replacement dose has been determined, followed by every 1 yearly thereafter (or more frequently depending on the clinical situation)
• T4
  • Pulse rate
  • Blood pressure
  • Clinical signs of hypo- and hyperthyroidism
• It is important to note that TSH should be measured to monitor and adjust the dose of thyroid replacement. TSH may be elevated during the first few months of treatment despite the patient being clinically euthyroid.
• In patients with low T4 and normal TSH levels, free T4 should be measured to decide about dosage adjustment.
• Likewise in patients with central hypothyroidism caused by a pituitary disorder, free T4 (unbound T4 should be measured to adjust the dose.

How to administer Thyroid extract?

Oral: Should be taken on an empty stomach to increase absorption (eg, 30minutes to 1 hour before breakfast).

Mechanism of action of Thyroid extract (Armour thyroid):

• T3 (triiodothyronine) is the primary active compound.
• It may be converted from T4 and circulates throughout the body to influence the growth and maturation.
• The exact mechanism of action is unknown.
• However, it is believed that thyroid hormone controls DNA transcription and protein synthesis as well as exerting its metabolic effects.
  • Normal metabolism
  • Growth and development
  • Promotion of gluconeogenesis
  • Glycogen storage is being used and mobilized more efficiently
  • Stimulation of protein production
  • BMR (basal metabolism rate) increased

The beginning of action: Liothyronine T3: Nearly 180 minutes

AbsorptionThyroxine (T4): 40 to 80% & 95% T3: T4 and T3 are the most common forms of Thyroxine. T3 is found in desiccated thyroid, which contains T4, T3, iodine that's mainly in the bound form, and T4.

Protein bindingT4: More than 99% of plasma proteins, including thyroxine binding globulin, prealbumin and albumin, are bound to it.

Metabolism: Undergoes metabolism in the liver to triiodothyronine (active); almost 80% T4 deiodinated in kidney and periphery; may also undergo glucuronidation/conjugation & enterohepatic recirculation

Half-life elimination: T4 :

• Euthyroid: 6 to 7 days;
• Hyperthyroid: 3 to 4 days;
• Hypothyroid: 9 to 10 days
• T3: 0.75 days

Time to peak: Serum: T4: 2 to 4 hours; T3: 2 to 3 days

Excretion: Excreted mainly via urine (major route of elimination) & partially undergoes excretion via feces

International Brand Names of Thyroid extract:

• Armour Thyroid
• Nature-Throid
• NP Thyroid
• Westhroid
• WP Thyroid

Thyroid extract Brand Names in Pakistan:

No Brands Available in Pakistan.