Chemistry - Obtained from bovine anterior pituitary glands, thyrotropin is a highly purified preparation of thyroid-stimulating hormone (TSH ). Thyrotropin is a glycoprotein and has a molecular weight of approximately 28,000 - 30,000. Thyrotropin is measured in International Units (IU), with 7.5 micrograms of thyrotropin approximately equivalent to 0.037 units. Commercially available thyrotropin is available as a lyophilized powder for reconstitution and is practically free of any adrenocorticotropic, somatotropic, gonadotropic and posterior pituitary hormones. Thyrotropin may also be known as TSH, thyrotrophin , thyroid-stimulating hormone or thyrotropic hormone .
Storage/Stability/Compatibility - Thyrotropin lyophilized powder for injection is reportedly stable in the dry state. However, the veterinary manufacturer recommends storing the powder below 59°F, and after reconstituting, storing in the refrigerator and discarding any unused drug after 48 hours. However, recent information has suggested that reconstituted TSH is stable for at least 3 weeks when refrigerated. The human-approved product may be kept refrigerated (2-8°C) for up to 2 weeks after reconstituting.
Pharmacology - Thyrotropin increases iodine uptake by the thyroid gland and increases the production and secretion of thyroid hormones. With prolonged use, hyperplasia of thyroid cells may occur.
Uses/Indications - The labeled indications for Dermathycin® (Coopers/P/M; Mallinckrodt) is for “the treatment of acanthosis nigricans and for temporary supportive therapy in hypothyroidism in dogs.” In actuality however, TSH is used in veterinary medicine principally as a diagnostic agent in the TSH stimulation test to diagnose primary hypothyroidism.
Pharmacokinetics - No specific information was located; exogenously administered TSH apparently exerts maximal increases in circulating T4 approximately 4-8 hours after IM or IV administration.
Contraindications/Precautions - The veterinary manufacturer (Coopers) lists adrenocortical insufficiency and hyperthyroidism as contraindications to TSH use for treatment purposes in dogs. In humans, TSH is contraindicated in patients with coronary thrombosis, hypersensitive to bovine thyrotropin, or with untreated Addison’s disease.
Adverse Effects/Warnings - Because the product is derived from bovine sources, anaphylaxis may occur in patients sensitive to bovine proteins, particularly with repeated use.
Overdosage - Chronic administration at high dosages can produce symptoms of hyperthyroidism. Massive overdoses can cause symptoms resembling thyroid storm. Refer to the levothyroxine monograph for more information on treatment.
Drug Interactions; Drug/Laboratory Interactions - For reference, refer to the information listed in the Levothyroxine monograph for more information.
For TSH stimulation test:
a) Draw pre-dose sample, then 5 - 10 IU of bovine TSH IV. Draw follow-up samples 4-8 hours after dosing. Normal thyroid gland should produce a 2-4 times increase in serum T3 and T4 levels. (Chen and Li 1987)
Client Information - Usually TSH will be used by professional staff. If the drug is to be used at home, the owner should follow directions carefully, shake the vial well after reconstituting, and store in the refrigerator.
Dosage Forms/Preparations/FDA Approval Status -
Thyroid Stimulating Hormone (Veterinary) 5 IU per vial (with 5 ml of Water for Injection as diluent); Dermathycin® (Schering Plough); (Rx) Approved for use in dogs. This product may not be currently on the market.
Thyrotropin (Thyroid Stimulating Hormone) Powder for Injection 10 IU per vial (with diluent); Thyrotropar® (Armour); (Rx)
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