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Thyrotropin Alfa

Pronunciation

(thye roe TROH pin AL fa)

Index Terms

  • Human Thyroid Stimulating Hormone
  • Recombinant Human Thyrotropin
  • Rh-TSH
  • Thyrotropin Alpha
  • TSH

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Solution Reconstituted, Intramuscular:

Thyrogen: 1.1 mg (1 ea)

Brand Names: U.S.

  • Thyrogen

Pharmacologic Category

  • Diagnostic Agent

Pharmacology

Thyrotropin alfa, derived from a recombinant DNA source, has the identical amino acid sequence as endogenous human thyroid stimulating hormone (TSH). As a diagnostic tool in conjunction with serum thyroglobulin (Tg) testing, thyrotropin alfa stimulates the secretion of Tg from any remaining thyroid tissues (remnants). Under conditions of successful thyroidectomy and complete ablation, very little serum Tg should be detected under TSH stimulatory conditions; conversely, elevated Tg levels suggest the presence of remnant thyroid tissues. Since the source of TSH is exogenous, stimulation of Tg synthesis can be achieved in euthyroid patients, avoiding the need for thyroid hormone withdrawal.

As an adjunctive agent for radioiodine ablation treatment of thyroid cancer tissue remnants, thyrotropin alfa binds to TSH receptors on these tissues, stimulating the uptake and organification of iodine, including radiolabeled iodine (I131). Cancerous tissue is destroyed via gamma emission from the radioiodine concentrated in these tissues.

Time to Peak

Median: 10 hours (range: 3-24 hours)

Half-Life Elimination

25 ± 10 hours

Use: Labeled Indications

Diagnostic imaging: Adjunctive diagnostic tool for serum thyroglobulin (Tg) testing (with or without radioiodine imaging) in follow up of patients with well-differentiated thyroid cancer who have previously undergone thyroidectomy.

Limitations of use: Thyrotropin alfa-stimulated Tg levels are generally lower than and do not correlate with Tg levels after thyroid hormone withdrawal; even when thyrotropin alfa-stimulated Tg testing is performed in combination with radioiodine imaging, there is a risk of missing a thyroid cancer diagnosis or of underestimating disease extent; anti-Tg antibodies may confound Tg assay and render Tg levels uninterpretable, in such cases, even with a negative or low-stage thyrotropin alfa radioiodine scan, consider further patient evaluation.

Thyroid tissue remnant ablation: Adjunctive treatment for radioiodine ablation of thyroid tissue remnants after total or near-total thyroidectomy in patients with well-differentiated thyroid cancer without evidence of metastatic disease

Limitations of use: The effect of thyrotropin alfa on long-term thyroid cancer outcomes has not been determined. Due to relatively small clinical experience, it is not possible to conclude if long-term thyroid cancer outcomes would be equivalent after thyrotropin alfa use or withholding thyroid hormone for TSH elevation prior to remnant ablation.

Contraindications

U.S. labeling: There are no contraindications listed in the manufacturer's labeling.

Canadian labeling: Hypersensitivity to thyrotropin alfa or any component of the formulation.

Dosing: Adult

Note: Consider pretreatment with glucocorticoids for patients in whom local tumor expansion may compromise vital anatomic structures (such as trachea, CNS, or extensive macroscopic lung metastases).

Diagnostic imaging: IM: 0.9 mg, followed 24 hours later by a second 0.9 mg dose; obtain serum Tg sample 72 hours after the second thyrotropin alfa injection

Thyroid tissue remnant ablation: IM: 0.9 mg, followed 24 hours later by a second 0.9 mg dose.

Radioiodine administration should be given 24 hours following the second thyrotropin alfa injection (for diagnostic scanning and remnant ablation). Perform diagnostic scanning 48 hours after radioiodine administration (72 hours after the second thyrotropin alfa injection). Post-therapy scanning may be delayed (additional days) to allow decline of background activity.

Dosing: Geriatric

Refer to adult dosing.

Dosing: Renal Impairment

There are no dosage adjustments provided in the manufacturer’s labeling; however, elimination is significantly slower in dialysis-dependent end-stage renal impairment and TSH level elevation may be prolonged.

Dosing: Hepatic Impairment

There are no dosage adjustments provided in the manufacturer's labeling (has not been studied).

Reconstitution

Reconstitute each vial with 1.2 mL of sterile water for injection to a concentration of 0.9 mg/mL. Gently swirl vial until dissolved; do not shake. Reconstituted solution should be clear and colorless; do not use if cloudy or discolored.

Administration

Administer only by IM injection into the buttock. Do not administer intravenously.

Storage

Store intact vials at 2°C to 8°C (36°F to 46°F). Protect from light. May store reconstituted solution for up to 24 hours between 2°C and 8°C (36°F and 46°F); avoid microbial contamination. If reconstituted solution is not refrigerated, use within 3 hours. Discard unused portion of the vial.

Drug Interactions

There are no known significant interactions.

Test Interactions

Thyroglobulin assay may be confounded by thyroglobulin antibodies, possibly leading to misinterpreted or difficult to interpret thyroglobulin levels. Routine measurement of TSH levels after thyrotropin alfa use is not recommended.

Adverse Reactions

>10%:

Gastrointestinal: Nausea (3% to 12%)

1% to 10%:

Central nervous system: Headache (1% to 7%), dizziness (≤3%), fatigue (1% to 3%), insomnia (≤2%), paresthesia (≤2%)

Endocrine & metabolic: Hypercholesterolemia (≤3%), blood cholesterol abnormal (≤1%)

Gastrointestinal: Vomiting (1% to 3%), diarrhea (≤1%)

Neuromuscular & skeletal: Weakness (≤2%)

Respiratory: Nasopharyngitis (≤1%)

Adverse reactions that may be related to local edema or hemorrhage at metastatic sites: Exacerbation of papillary carcinoma (enlargement of locally-recurring papillary carcinoma, accompanied by dyspnea, stridor, or dysphonia), hemiparesis, hemiplegia, laryngeal edema (with respiratory distress), pain, sudden blindness

<1% (Limited to important or life-threatening): Antibody development to thyrotropin alfa, atrial arrhythmia, cerebrovascular accident, hypersensitivity reaction (eg, dyspnea, flushing, pruritus, skin rash, urticaria), myocardial infarction, pain, weakness (unilateral)

Warnings/Precautions

Concerns related to adverse effects:

• Hyperthyroidism: Thyrotropin alfa use may cause a transient (over 7 to 14 days) and significant rise in serum thyroid hormone concentration in patients with substantial in situ thyroid tissue or with functional thyroid cancer metastases. Thyrotropin alfa–induced hyperthyroidism may result in serious complications in patients with certain risk factors (heart disease, extensive metastatic disease or with underlying serious illness); consider hospitalization for administration and subsequent observation. Deaths within 24 hours of thyrotropin alfa administration have been reported.

• Stroke: Postmarketing reports of stroke or symptoms suggestive of stroke (eg, unilateral weakness) have occurred within 3 days of administration in patients without known central nervous system metastases. A majority of these patients had risk factors for stroke (eg, smokers or history of migraine) or were young women taking oral contraceptives. Patients should be well hydrated prior to administration.

• Tumor growth: Sudden, rapid, and painful growth of residual thyroid tissue or distant metastases may occur following thyrotropin alfa administration. Symptoms are associated with tissue location and include acute hemiplegia, hemiparesis, and vision loss 1 to 3 days after administration. Laryngeal edema, pain at site of distant metastases, and respiratory distress requiring tracheotomy have also been reported. Consider glucocorticoid premedication in patients where local tumor enlargement may compromise vital structures (trachea, CNS, or extensive macroscopic lung metastases).

Disease-related concerns:

• Cardiovascular disease: Patients with known history of heart disease in the presence of significant residual thyroid tissue are at increased risk for thyrotropin alfa-induced hyperthyroidism.

• Renal impairment: Thyrotropin alfa elimination is significantly reduced in dialysis-dependent end-stage renal impairment, leading to prolonged elevation of TSH levels.

Special populations:

• Elderly: Elderly patients with residual thyroid tissue are at increased risk for thyrotropin alfa-induced hyperthyroidism

Monitoring Parameters

Neurologic adverse events (hemiplegia, hemiparesis, stroke, weakness); dyspnea, dysphonia, stridor or other symptoms of local tumor growth

Pregnancy Risk Factor

C

Pregnancy Considerations

Animal reproduction studies have not been conducted. Effects on the fetus or pregnant woman are unknown.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience nausea or vomiting. Have patient report immediately to prescriber signs of severe cerebrovascular disease (change in strength on one side is greater than the other, trouble speaking or thinking, change in balance, or change in eyesight), angina, tachycardia, shortness of breath, severe dizziness, passing out, or severe headache (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

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