Thyroid hormones (THs) control normal brain development and function in humans, and identifying environmental thyroid disrupting chemicals has significant public health implications. As such, some developmental and reproductive toxicology studies now require or suggest serum total thyroxine (T4) measurements in pregnant, lactating, and developing rats. However, serum T4 concentrations are normally low in the fetus and pup which makes accurate quantification difficult. These challenges can be circumvented by technologies like mass spectrometry, but these approaches are expensive and not always widely available. To demonstrate the feasibility of measuring serum T4 using a commercially available kit we compare T4 concentrations in pregnant, fetal, and neonatal rats, as measured by both liquid chromatography mass spectrometry (LC/MS/MS) and radioimmunoassay (RIA). The sera samples analyzed were obtained from rats on gestational day 20 (dams and fetuses) or postnatal day 5 (pups), following a maternal exposure to the goitrogen propylthiouracil (0-3 ppm) to incrementally decrease T4. We show that with optimization, it is possible to measure serum T4 using low sample volumes (25-50μL) by RIA and the relative control values obtained are comparable to LC/MS/MS. This work demonstrates that low concentrationT4 quantification is feasible for toxicological studies, but attention to technical detail is pertinent.

This dataset is associated with the following publication: O'Shaughnessy, K., M. Hotchkiss, A. Buckalew, A. Murr, M. Gilbert, and T. Stoker. An optimized radioimmunoassay for quantification of total serum thyroxine (T4) in fetal, neonatal, and pregnant rats. NEUROTOXICOLOGY AND TERATOLOGY. Elsevier Science Ltd, New York, NY, USA, 100: 107303, (2023).