Thyrotropin Alfa

Pronunciation: THYE-roe-TROE-pin AL-fa
Class: Thyroid function test

Trade Names

Thyrogen
- Injection, lyophilized powder for solution 1.1 mg

Pharmacology

Thyrotropin alfa has comparable biochemical properties to human pituitary thyroid-stimulating hormone (TSH). Binding to TSH receptors on normal thyroid epithelial cells or on well-differentiated thyroid cancer tissue stimulates iodine uptake and organification, and synthesis and secretion of thyroglobulin, triiodothyronine, and thyroxine.

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Pharmacokinetics

Absorption

C max is 116 mU/L. T max is 3 to 24 h.

Elimination

Mean elimination t ½ is 25 ± 10 h.

Indications and Usage

Adjunctive diagnostic tool for serum thyroglobulin testing with or without radioiodine imaging in the follow-up of patients with well-differentiated thyroid cancer; adjunctive treatment of radioiodine ablation of thyroid tissue remnants in patients who have undergone a near-total thyroidectomy for well-differentiated thyroid cancer and who do not have evidence of metastatic cancer; may be used in patients with an undetectable thyroglobulin upon thyroid hormone suppressive therapy to exclude residual or recurrent thyroid cancer; may be used in combination with radioiodine to ablate thyroid remnants following near-total thyroidectomy in patients without evidence of metastatic disease; may be used in patients requiring serum thyroglobulin testing and radioiodine imaging who are unwilling to undergo thyroid hormone withdrawal testing and whose treating health care provider believes that the use of a less sensitive test is justified; may be used in patients who are either unable to mount an adequate endogenous TSH response to thyroid hormone withdrawal or in whom withdrawal is medically contraindicated.

Contraindications

Standard considerations.

Dosage and Administration

Adults and Children 16 yr of age and older

IM 0.9 mg initially, followed by 0.9 mg 24 h later.

General Advice

  • Not for IV use.
  • Consider pretreatment with glucocorticoids for patients in whom local tumor expansion may compromise vital anatomic structures (eg, trachea, CNS, or extensive macroscopic lung metastases).
  • After reconstitution with 1.2 mL of sterile water for injection, 1 mL is administered to the buttock.
  • For radioiodine imaging or remnant ablation, give radioiodine 24 h following the final thyrotropin injection.
  • Perform diagnostic scanning 48 h after radioiodine administration, whereas posttherapy scanning may be delayed additional days to allow background activity to decline.
  • For serum thyroglobulin testing, obtain the serum sample 72 h after the final thyrotropin alfa injection.

Storage/Stability

Store at 36° to 46°F. The reconstituted solution may be stored for up to 24 h at 36° to 46°F. Protect from light.

Drug Interactions

None well documented.

Laboratory Test Interactions

Thyroglobulin antibodies may confound the thyroglobulin assay, making levels uninterpretable. In this case, patients should be further evaluated.

Adverse Reactions

Cardiovascular

Atrial arrhythmias (postmarketing).

CNS

Headache (7%); dizziness, fatigue (3%); asthenia, insomnia, paresthesia (2%).

EENT

Nasopharyngitis (1%); laryngeal edema with respiratory distress, visual loss (postmarketing).

GI

Nausea (12%); vomiting (3%); diarrhea (1%).

Hypersensitivity

Hypersensitivity reactions, including flushing, pruritus, rash, respiratory signs and symptoms, and urticaria (postmarketing).

Musculoskeletal

Hemiparesis, hemiplegia (7%).

Miscellaneous

Thyroglobulin present (1%); death, rapid and painful enlargement of locally recurring papillary carcinoma accompanied by dyspnea, dysphonia, and stridor; transient flu-like symptoms (postmarketing).

Precautions

Pregnancy

Category C .

Lactation

Undetermined.

Children

Safety and efficacy not established in children younger than 16 yr of age.

Elderly

Palpitations or cardiac rhythm disorder may occur in high-risk elderly patients with functioning thyroid tumors undergoing thyrotropin administration.

Renal Function

Thyrotropin elimination is slower in dialysis-dependent end-stage renal disease patients, resulting in prolonged TSH levels.

Special Risk Patients

Patients with known heart disease, extensive metastatic disease, or other known serious underlying illness should be hospitalized for administration of thyrotropin because thyrotropin-induced hyperthyroidism could have serious consequences.

Death

There have been reports of death in which events leading to death occurred within 24 h of thyrotropin alfa administration.

Heart disease

Transient but important increases in serum thyroid hormone concentration have occurred when thyrotropin was given to patients with substantial thyroid tissue present in situ. Use with caution in patients with a known history of heart disease and residual thyroid tissue.

Hypersensitivity

Use with caution in patients who have been previously treated with bovine TSH, particularly patients who have experienced hypersensitivity to bovine TSH.

Overdosage

Symptoms

Dizziness, headache, hot flashes, nausea, vomiting, and weakness have been reported with doses that were higher than recommended.

Copyright © 2009 Wolters Kluwer Health.

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