Effect of Thyro-Parathyroidectomy in New Born Rats. ∗

Abstract

Rats are particularly adapted for experiments on the effect of very early ablation of the thyroid because they are very immature at birth, and have had a developed thyroid only the last 3 days in utero. 1 No previous reports on mammals have dealt with such early ablations. The present experiments deal with the removal of the thyro-parathyroid apparatus in young rats on the first or second day of life. A very few animals were also operated on the seventh and fourteenth days of life. Complete removal is extremely difficult because of the gelatinous consistency of the infantile tissues. Every animal here reported was checked for completeness of removal by microscopic examination of serial sections of the tracheal region made at autopsy. This check was found to be absolutely necessary since in many stunted animals microscopic remnants were found. These will be treated separately as “incompletes.”

Of 486 rats thyro-parathyroidectomized on the first or second day of life, 167 survived the critical period of the first post-operative week. Animals were sacrificed at various intervals after data on growth had been secured. The 167 survivors were autopsied and 107 of them have teen examined for completeness of removal. Twenty of these show no remnant of the thyro-parathyroid apparatus. Of the 46 animals operated on at 7 or 14 days, verifying examination of the operative field had been completed on only 5. In an operated control series of 38 animals, the thyro-parathyroids were removed on the first day and the glands re-implanted in the same animal 2 ; 30 survived beyond the critical week; 28 showed normal growth curves. Some of them have not yet been sacrificed for examination. These animals show that the operation itself is not a factor in causing a retardation of development.