[The effect of laryngectomy and postoperative radiotheraphy on thyroid gland functions]

We investigated the frequency of hypothyroidism in patients treated with total laryngectomy, hemithyroidectomy-isthmectomy, and postoperative radiotherapy for T3 or T4 larynx cancers.

Twenty-nine male patients (mean age 54 years; range 43 to 72 years) with T3 or T4 larynx cancers were prospectively included in the study. Preoperatively, thyroid function tests were normal in all the patients. Following radiotherapy, serum thyroid-stimulating hormone (sTSH), free triiodothyronine (FT3), and free thyroxine (FT4) levels were measured every three months at least for a year. Detection of an increased level of sTSH together with decreased or normal levels of FT3 and/or FT4 indicated clinical and subclinical hypothyroidism, respectively. The relationship was assessed between hypothyroidism and both age and radiotherapy dosage. Statistical analyses were made with the use of the Student's t- test and Mann-Whitney U-test.

Following radiotherapy, thyroid function tests remained normal in 12 patients (41%), while 12 patients (41%) and five patients (18%) developed subclinical and clinical hypothyroidism, respectively. No significant relationship was found between age and thyroid dysfunction (p>0.05), whereas radiotherapy dosage was found in significant relationship with the development of hypothyroidism (p<0.05).

Due to high rates of subclinical or clinical hypothyroidism following combined therapy, thyroid functions should be closely monitored in patients undergoing laryngectomy for T3 or T4 larynx cancers.