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Growth and transformation of the mandibular joint in the rat thyroidectomized at birth

1953; Elsevier BV; Volume: 39; Issue: 8 Linguagem: Inglês

10.1016/0002-9416(53)90077-3

1557-8488

Louis J. Baume, Hermann Becks, Herbert M. Evans,

Craniofacial Disorders and Treatments

Abstract In order to assess the effects of the thyroid gland on the structures of the mandibular joint, a roentgenographic and histologic study was carried out with four groups of experimental rats which were thyroidectomized at birth and sacrificed at 63 days of age. One group served as thyroidectomized controls, another was given pure pituitary growth hormone for thirty-one days, the next group was supplemented with thyroxin for the same period of time, and the last group was treated with both growth hormone and thyroxin. A series of normal 63-day-old rats were used as normal controls. 1. 1. The thyroidectomized rats showed dwarfed and deformed mandibular joint structures incomparable to any age controls. The prominent histologic defects consisted of stunted chondrogenesis and nearly arrested cartilage erosion and depressed modeling resorption. 2. 2. Growth hormone restored the mandibular dimensions by virtue of marked activation of chondrogenesis and membranous osteogenesis. As chondroclasia and osteoclasia, however, remained deficient, the joint structures exhibited a juvenile, immature appearance. 3. 3. Thyroxin administration promoted maturation of the mandibular condyle to the extent of the normal age controls, but without restoring the normal mandibular dimensions or even those of the growth hormone-treated group. These significant findings are at variance with those made in the tibias and may be attributed to the fact that in the absence of the thyroid gland, growth hormone does not seem to be able to promote endochondral ossification, but stimulates, for the main part, chondrogenesis and periosteal bone formation. 4. 4. Combined supplement of growth hormone and thyroxin elicited an increase in size over the extent of any of the previous groups to almost normal size, while maturation was accelerated more than in the growth hormone-injected group, but less than in the thyroxin-treated group. Experimental evidence thus is procured that proper mandibular development and a good facial pattern are dependent upon normal thyroid function. Severe thyroid deficiency during the growth periods causes stunting and discordance of the growth processes at the condylar head. Thyroxin supplement proves to be unable to restore full normal dimension, apparently on account of a hypophyseal syndrome which is only partly reversible. Combined treatment with growth hormone and thyroxin showed the best results in the control of thyroprivic mandibular symptoms.