PURPOSE: Hypothyroidism is a common situation among the aged which affects protein synthesis. The objective of the present study was to determine the influence of hypothyroidism on the healing process in aged rats. METHODS: 96 male Wistar rats were used, 48 of them with a mean age of 110 days and 48 with a mean age of 750 days. Half the young animals and half the old ones were euthyroid and half were hypothyroid. Hypothyroidism was obtained by total thyroidectomy. Thirty days after surgery the animals were submitted to median laparotomy followed by laparorrhaphy on 2 synthesis planes. Six animals from each group were submitted to euthanasia by drawing lots on the 3rd, 7th and 14th postoperative day and submitted to macroscopic, resistance, and histopathological analysis. RESULTS: The resistance of the skin scars was lower in hypothyroid animals, both the young (p=0.0145) and old (p=0.0242) ones, with no significant relation with age being detected. The resistance of the scars on the peritoneum-muscle-aponeurosis plane was lower in old animals on the 24th day (p=0.0014) and even lower in hypothyroid old animals (p=0.0000). The histological evolution was similar, but differences in collagen presence were observed. On the 7th day the skin scars had a lower collagen content in young (p=0.0201) and old (p=0.0003). hypothyroid animals. On the 14th day the scars of old hypothyroid animals had less collagen than those of normal old animals (p=0.0092) and those of young hypothyroid animals (p=0.0283). On the 3rd day, the scars of hypothyroid animals on the peritoneum-muscle-aponeurosis plane presented less collagen than those of both young (p=0.0089) and old (p=0.0171) normal controls, but there was no relation with age. This association persisted on the 7th and 17th day, but age dependence was observed at these time points. CONCLUSION: Analysis of the results permits us to conclude that healing is impaired in the presence of hypothyroidism and worsens with aging.
Wound healing; Collagen; Hypothyroidism; Aging
