Ulsenius was primarily a physician, but also concerned himself with the nature of medicine and doctors in Renaissance society. In Nuremberg he overturned the medieval Galenic classifications and reorganised the university medical curriculum. Regarding the role of physician as equal to that of humanistic scholars, Ulsenius proposed the role of a doctor as requiring a high ethical standard, beyond fiscal rewards. During the German syphilis epidemic of 1496 he published a poem approaching the disease from both medical and astrological perspectives.
Bryan S Turner, Review of C G. Santing, Geneeskunde en humanisme. Een intellectuele biografie van Theodericus Ulsenius (c 1460-1508), Rotterdam: Erasmus Publishing, 1992, in Social History of Medicine 7, 1994.