Barnes believed that a reading over 98.2 °F (36.8 °C) was indicative of hyperthyroidism, unless a patient had advanced arthritis, which he claimed would falsely elevate the temperature due to muscle contractions.

[3] The test has never been adopted by the medical profession; however, it was subsequently promoted by Barnes in a series of books, and is currently advocated by some alternative medicine practitioners.

[12] In his books, Barnes argued that hypothyroidism affected more than 40% of the American population,[3][5] significantly higher than the prevalence of approximately 5% reported in the peer-reviewed medical literature.

He recommended starting with a small dose, and then slowly increasing the dosage in monthly intervals until symptoms resolved and waking body temperature was between 97.8F and 98.2F.

[3][5] In 1932, W. Fleischmann and S. Kann reported in a German gestational physiology journal[14] that female bitterings, small carp-like fish, "show an enlargement of the ovipositor following injection of an estrogenic preparation".

Aaron E. Kanter, Carl P. Bauer and Arthur H. Klawans of the University of Chicago added a teaspoon of urine from a pregnant woman to a bowl in which a bitterling was swimming.

They sought to determine the source organ of whatever non-pregnant urine substance was causing the same bitterling ovipositor response as Fleischmann's estrogenic preparation.

[15] In 1938, Fleischmann and Kann determined that in addition to estrogen, a specific adrenal hormone, corticosterone, could cause the observed bitterling ovipositor reaction.

[14] This additional non-pregnant hormone reaction made the bitterling test not useful for its originally announced purpose, though it did open the door to an investigation of why corticosterone is significant in urine.