Graded cryohypophysectomy in the rhesus monkey

Abstract

✓ Histopathology and endocrine function of the pituitary gland of rhesus monkeys subjected to graded cryohypophysectomy were compared with the histopathology and endocrine function in hypophysectomized and sham-operated monkeys. Freezing at −50°, −100°, and −150°C destroyed 72.3%, 78.3%, and 93.1% of the pituitary respectively. The posterior lobe was more resistant to the damaging effects of cold. A nearly complete (96.3%) histological hypophysectomy was accomplished at −190°C; nearly all remaining viable tissue was in the posterior lobe. Freezing at −150°C appears to result in a complete functional hypophysectomy. Of the adenohypophyseal cells, the gonadotropin-secreting cells were the most susceptible to cold, with the growth-hormone-producing cells next in susceptibility. Adrenocorticotropin-secreting cells were more resistant. Cells producing thyroid-stimulating hormones were not susceptible, and the pituitary stalk was quite resistant to the damaging effects of freezing at these temperatures. Thus, a predictable partial hypophysectomy by means of cryosurgery seems feasible, and, with a predetermined time, it is evident that the degree of cold is critical in achieving a complete cryohypophysectomy.