Compensatory Hypertrophy of Thymus Gland

We recently have reported several studies concerning the marked stimulation of growth and regeneration that occurs in the thymus gland of rats, of any age, following double suprarenalectomy (1-3). We showed that, as the result of such a procedure, marked hyperplasia of the involuting thymus, with enlargement of the same, occurs with great constancy. In line with these studies, we undertook a series of transplantation experiments which involved the carrying out of over 100 thymectomies in rats about the age of puberty or younger. In the course of this work, it was frequently noted that when a small, non-traumatized fragment of the gland was accidently left behind at operation, autopsy disclosed a fairly large regenerated mass, even as early as 2 weeks after the partial thymectomy. But this evidence was indirect as we had no means of accurately measuring the fragment accidently left. These incidental findings suggested that the gland was probably capable of undergoing very rapid compensatory hypertrophy as wen as regeneration. A review of the extensive literature on the thymus shows that no positive evidence of uncomplicated compensatory hypertrophy has been obtained.