Hypothyroidism in head and neck cancer patients: Experimental and clinical observations

Abstract

Damage to the thyroid gland may occur in patients undergoing treatment for head and neck neoplasms. This injury may result from damage incurred during surgery, from radiation therapy, or a combination of the two. Development of hypothyroidism is often insidious with potential harmful effects. An experimental study was performed to study the effects of hypothyroidism in pigs whose skin closely approximates that of the human. Wound tensile strength and flap necrosis were studied in the hypothyroid animal treated by surgery, radiation, and a combination of the two. The results of this study indicate that hypothyroidism alone has no significant unfavorable impact on wound tensile strengths or flap survival. When combined with preoperative radiation, however, there are statistically significant deleterious effects on both wound tensile strengths and flap survival. Histologically, collagen fibers within the wound appear shorter and thinner, which probably accounts for decreased wound tensile strengths. A clinical review of 62 head and neck cancer patients was also conducted. Within the study group, 10% of patients developed abnormally low thyroxine measurements, whereas 15% developed high thyroid-stimulating hormone levels as the only evidence of early primary hypothyroidism. Hypothyroidism was not statistically related to tumor size, nodal status, clinical staging, or treatment group (surgery alone, radiation alone, or combination surgery and radiation). A previously unreported finding is that patients who develop a second primary tumor are significantly at risk for developing hypothyroidism. All patients diagnosed with a head and neck cancer should undergo baseline thyroid function testing, including measurement of TSH, and have serial repeat testing after treatment. Thyroid function determination should be mandatory in patients undergoing oncologic salvage procedures or treatment of a second primary tumor.

Wound Healing in Colonic Anastomosis in Hypothyroidism

“…Unfortunately, our search for bibliographical references in English to GI healing and hypothyroidism was unsuccessful. Hypothyroidism can be induced by TT, antithyroid drugs or cervical radiation [3,5,6,11,16,19,22,31,48] . In the present study, TT was performed to induce uniform and efficacious hypothyroidism, thus avoiding the occasional side effects of antithyroid drugs, such as hepatic necrosis (caused by propylthiouracil), cholestasis (caused by methimazole), alterations of the immune system, with an eventual decrease in lymphocytic response, and occasional agranulocytosis [33,[58][59][60][61] .…”

“…These hormones also play a part in the healing process as they interfere with fibroblast function [2,3] , accelerating the formation of collagen or promoting collagenolysis [4,5] . In several studies of cutaneous healing, it was observed that hypothyroidism could prolong the proliferative phase of healing as well as alter the quality of collagen, forming thinner and smaller collagen fibers [6][7][8] . Thyroxin administration can induce protein synthesis, improving the oxidation and phosphorylation of the mitochondria, thus reversing the negative effects of hypothyroidism on the healing process [9] .…”

“…The impairment of cutaneous wound healing has been demonstrated in individuals with hypothyroidism induced by antithyroid drugs [42][43][44][45] , thyroid radiation [6] or surgical ablation [3,5] , together with the role of thyroid hormone replacement in improving the healing process [45][46][47] .…”

Thyroid hormone action on skin

“…46 There are also reports of hypothyroid patients who required thyroid hormone to achieve healing of radiation induced neck fistulae. 49,50 Conversely, Cannon 49 reported that hypothyroidism did not diminish wound strength in pigs and Ladenson et al 50 did not detect wound healing deficits in hypothyroid humans.…”

Tracheal suture in rats with hypothyroidism: wound healing study

“…Alterations in the cicatricial process have been described in patients who presented hypothyroidism gravis, resulting from total thyroidectomy or from cervical radiotherapy 4,5 . Thyroid hormones have an important role in the growth and development of organs and tissues, essential to the maintenance of life quality 6 .…”