Measurements of adrenal corticosteroids were performed at the Michigan State University Veterinary Diagnostic Laboratory, which is an American Association of Veterinary Laboratory Diagnosticians accredited laboratory. Plasma or serum aldosterone concentrations were measured with a commercially available radioimmunoassay kit (ACTIVE Aldosterone RIA, Beckman Coulter, IMMUNOTECH s.r.o., Prague, Czech) in 9 of the 10 cats. Serum progesterone concentrations were measured in the same 9 cats with a commercially available competitive chemiluminescent immunoassay (Immulite 2000 Progesterone, Siemens Healthcare Diagnostics Ltd, Gwynedd, UK) that has been described by others for use in cats.16 (link), 17 (link) Cortisol concentrations also were determined using a chemiluminescent immunoassay (Immulite 2000 Cortisol, Siemens Healthcare Diagnostics Ltd) that has been described for use in cats.18 (link) Detailed descriptions of these assays as well as the assay for corticosterone measurements are available in Supporting Information Appendix 1. Corticosteroid measurements in 1 cat were performed before 2015, and different radioimmunoassay kits were being used in our laboratory (Coat‐a‐Count, Siemens Medical Solutions Diagnostics, Los Angeles, California) at that time. Descriptions of the assays used for hormones measurements in this cat can be found elsewhere.9 (link)