THYROTROPIN (THYROID-STIMULATING HORMONE; TSH)

Chemistry - Obtained from bovine anterior pituitary glands, thyrotropin is a highly purifiedpreparation of thyroid-stimulating hormone (TSH). Thyrotropin is a glycoprotein and has amolecular 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. Commerciallyavailable thyrotropin is available as a lyophilized powder for reconstitution and is practically free ofany adrenocorticotropic, somatotropic, gonadotropic and posterior pituitary hormones.
Thyrotropin may also be known as TSH, thyrotrophin, thyroid-stimulating hormone or thyrotropichormone.

Storage, Stability, Compatibility

Thyrotropin lyophilized powder for injection is reportedlystable in the dry state. However, the veterinary manufacturer recommends storing the powder below59°F, and after reconstituting, storing in the refrigerator and discarding any unused drug after 48hours. However, recent information has suggested that reconstituted TSH is stable for at least 3weeks when refrigerated. The human-approved product may be kept refrigerated (2-8°C) for up to 2weeks after reconstituting.

Pharmacology - THYROTROPIN (THYROID-STIMULATING HORMONE; TSH)

Thyrotropin increases iodine uptake by the thyroid gland and increases the production and secretion of thyroid hormones. With prolonged use, hyperplasia of thyroid cells mayoccur.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 indogs." In actuality however, TSH is used in veterinary medicine principally as a diagnostic agent inthe TSH stimulation test to diagnose primary hypothyroidism.

Pharmacokinetics - THYROTROPIN (THYROID-STIMULATING HORMONE; TSH)

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 bovinethyrotropin, or with untreated Addison's disease.

Adverse Effects, Warnings

Because the product is derived from bovine sources, anaphylaxismay 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 levothyroxinemonograph for more information on treatment.
Drug Interactions; Drug/Laboratory Interactions - For reference, refer to the information listedin the Levothyroxine monograph for more information.