A recent study maintains to have identified a case of severe Graves’ disease in the bronze statue of Cosimo I de’ Medici forged by Benevenuto Cellini (between 1545 and 1547). We carefully examined the artistic sources, the medical primary sources and the paleopathological findings with the aim of showing that Cosimo I de’ Medici (1519-1574) was not affected by severe Graves’ disease. The artistic analysis of different statues and portraits of the Grand-Duke of Tuscany confirms the medical interpretation. Cosimo I was thick-necked with a well-developed laryngeal prominence of the thyroid cartilage (Adam’s Apple) and slightly bulging eyes. Plagued by obesity, Cosimo I was affected by DISH (diffuse idiopathic skeletal hyperostosis), chronic malaria, and severe osteoarthritis. The Grand Duke had a stroke on February 18th 1568, aged 49, and suffered from the sequelae for six years. Previous scholars proposed chronic cerebral vasculopathy as a possible diagnosis. We surmise that, as in modern day obese patients with DISH, he had increased risk for cardiovascular morbidity. The presence of a familiar thick-neck and a well-developed Adam’s Apple can be observed in several other members of the Medici family such Giovanni dalle Bande Nere, Cosimo I de’ Medici’s father. The same features can also be found in several other predecessors of Cosimo I such as Piero the Gouty and his sons Lorenzo the Magnificent and Giuliano de’ Medici, Pope Leo X, Giuliano de’ Medici, Duke of Nemours and Lorenzo de’ Medici, Duke of Urbino. This paper shows that the combination of literary, artistic, paleopathological sources is fundamental to correctly assess disease manifestation. A constant interaction between anatomy and art is recommended so to avoid over-interpretation of pathologic conditions in personages of the past.