Envigo has developed and validated a robust analytical method to evaluate the potential effects on thyroid hormone levels in rat F1 offspring. It is now possible for the company to successfully determine levels of T3 (triiodothyronine) and T4 (thyroxine) hormones in serum from rats at days 4 and 13 of age using ultra high pressure liquid chromatography coupled to a high-end tandem mass spectrometer (UHPLC-MS/MS) for detection. As a result, OECD reproductive toxicology guidelines OECD 421, 422 and 443, which include an evaluation of thyroid function, can now be performed at Envigo. 

This highly sensitive method was successfully validated for the determination of T3 (5 to 1,500 pg/mL) and T4 (70 to 70,000 pg/mL) in rat serum for F1 animals at days 4 and 13 of age using a sample volume of 50 μL. Envigo is also able to perform detailed microscopic examination of the thyroid glands fromF1 offspring at day 13. In some instances, an evaluation of the potential effects on Thyroid Stimulating Hormone (TSH) levels in plasma for offspring at days 4 and 13 can also be undertaken using an immunoassay method.

Prior to this development, Envigo performed a PTU (Propylthiouracil) positive control developmental thyroid study as required by the U.S. Environmental Protection Agency (EPA). Quantifiable levels of TSH were detected in the plasma of pregnant female rats and their fetuses. In addition, quantifiable levels of T3 and T4 hormones were also detected in pregnant females, but the validated immunoassay technique was unable to detect T3 and T4 in foetuses. It was later shown that this was also the case for F1 offspring at days 4 and 13 of age. A substantial increase in sensitivity for detection of T3 and T4 levels was clearly required for F1 offspring before these hormones could be detected in control animals. As a result, Envigo developed and validated the UHPLC-MS/MS technique to overcome this serious challenge and thereby enable all relevant OECD and US EPA testing requirements to be met.

“At Envigo, we pride ourselves in taking a lead in developing solutions to scientific and technical challenges as they emerge in preclinical assays,” said John Handley, president EMEA operations, Envigo. “We have been keen to take a prominent role in the development of thyroid hormone assays and are therefore very pleased to make our high sensitivity UHPLC-MS/MS method available to the market.”