Midgut Malrotation in Adults

if "'5I therapy is used in these cases the thyroid gland will be permanently damaged and hypothyroidism will inevitably result. The problem then lies in identifying this group of patients beforehand rather than trying to reduce the dose of ...I. Hence, although a correlation between high thyroid antibody titres and post-radiation hypothyroidism has yet to be shown, it would seem wise not to treat these cases with 1311, since they are likely to " burn up " their own thyroid tissue. Further clues may be provided by an examination of serum levels of long-acting thyroid stimulator. On the other hand, radiobiological studies might suggest a different explanation. Following radiation mitosis may be delayed. Furthermore, latent cell damage and death may not be seen until long after irradiation, when the cell has subsequently entered one or more mitotic divisions. As time progresses the feedback stimulus of the failing thyroid gland induces the pituitary to release more thyroidstimulating hormone. Under this stimulus further thyroid cells enter division and die. This process could become a vicious circle, with increasing hypothyroidism causing increased cell destruction. This would correlate with the clinical findings of some workers who report' that the development of postradiation hypothyroidism is a continuing process, progressing at a rate of about 3% per annum. Again, it has been shown' that for rats, at any rate, a dose of radiation which results in a reduction of thyroid function inevitably interferes with the reproductive integrity of the gland. Although this may be an insoluble problem, it has been pointed out' ' that the irregular distribution of iodine in the thyroid gland may mean that some cells receive sublethal damage and are capable of recovery.-I am, etc., W. S. B. LOWRY. Northern Ireland Radiotherapy Centre, Purdysburn, Belfast.