- Pituitary-thyroid responsiveness to intramuscular thyrotropin-releasing hormone based on analyses of serum thyroxine, tri-iodothyronine and thyrotropin concentrations. Azizi, F., Vagenakis, A.G., Portnay, G.I., Rapoport, B., Ingbar, S.H., Braverman, L.E. N. Engl. J. Med. (1975)