July 24, 2002
Production of Thyrel®, TRH (protirelin), has been halted as of July 2002. The manufacturer, Ferring Pharmaceuticals, says that it is modifying the manufacturing process for Thyrel® in order to meet newly mandated production guidelines. Since the development of ultrasensitive TSH assays, the indications for use of TRH for thyroid axis testing have become fairly limited. TRH is now rarely indicated for detection of thyrotoxicosis or hypothyroidism. However, results from a TRH stimulation test can sometimes be useful in special clinical situations, such as distinguishing TSH-secreting pituitary tumors from other forms of inappropriate TSH secretion and in subtle cases of central hypothyroidism. It is uncertain how long this processing modification will take. Ferring’s information letter says , “Ferring will make every effort to implement these changes as soon as possible, but as with any pharmaceutical process, significant time is needed to make these manufacturing upgrades.” As no other company appears to produce TRH at this time, no replacement product is expected to be available until Thyrel® returns to the market.