One of his few times away from the University of Michigan was for an internship and residency at Cleveland City Hospital, where one of his assignments was a study of the use of an antithyroid drug in treatment of hyperthyroidism.
Early in his career, he established a clinic in which radioactive iodine was used to help diagnose and detect tumors in patients with hyperthyroidism and thyroid cancer.
He became an advocate for a therapy that combined radioiodine and surgery, which has been accepted by the medical profession as the standard regimen for diagnosis and treatment of thyroid conditions.
[3] Results of a study Beierwaltes reported in 1950 showed that he was able to use x-rays to prevent blindness in eight of eleven patients with a form of the disease exophthalmos.
The pituitary glands of these patients were believed to have been producing excessive amounts of thyroid-stimulating hormone which caused swelling in the eyesocket that could compress the optic nerve or ophthalmic artery leading to blindness.