While it is generally believed that cardiac disturbances in patients with goiter are caused by hyperthyroidism, attention has been called recently to heart disease in goitrous patients who do not present symptoms of increased thyroid function. Davison1 designated this condition as "masked hyperthyroidism." He assumed that adenomas are for years spilling over into the circulation toxic products which, though not sufficient to produce an increase of the basal metabolic rate at any time, cause low grade toxemia which ultimately produces heart disease.
Hertzler,2 on the other hand, denied that cardiac disturbances in patients with long-standing goiter are due to hyperthyroidism and expressed the belief that the colloid in old goiters degenerates and forms a substance which when resorbed acts specifically on the heart muscle. He found that this degenerated colloid stains orange with Mallory's aniline blue method in contrast to the blue-stained colloid in exophthalmic goiter.
HELLWIG CA. THE GOITER HEARTAN EXPERIMENTAL STUDY. Arch Surg. 1944;48(1):27-35. doi:10.1001/archsurg.1944.01230010030003