[Hemi-agenesis of the thyroid gland]

The paper is based on the observation of two cases of thyroid hemiagenesis, not so much for the rarity of the findings as for their diagnostic ambiguity. These aspects are discussed along with the consequent therapeutic problems. The concept of "no clinical significance" expressed elsewhere on the question of hemiagenetic thyroids is not shared because of possible development into goitre, myxoedema, Basedow's disease and, particularly, neoplastic degeneration. The congenitally incomplete organ is called on to sustain the entire functional burden from birth and even earlier. Where hemiagenesis is identified, this means careful supervision because it is precisely as a result of the organ's mutilated condition and the duration of the functional burden involved that the danger lies.