Endocrine Abstracts

Background: Hypothyroidism is a frequent side effect of external radiotherapy of the cervical region for head and neck cancer. Up to 33% of irradiated patients developed primary hypothyroidism within 2 years after radiation therapy. The risk of hypothyroidism increases with radiation dose.

Patients and methods: Four patients (2M/2F), aged 53.3±13.9 years, resident both in iodine sufficient (n=2) and iodine deficient areas (n=2), were diagnosed with hypothyroidism after cervical irradiation for head and neck cancer. TSH and FT₄ were measured by chemiluminescence.

Case reports: Patients received external-beam radiation therapy delivered in the form of photon beams, for undifferentiated cavum carcinoma, oropharyngeal cancer, epidermoid spinocellular carcinoma of palatine tonsil and laryngeal carcinoma; median radiation dose was 63 Gy. Median time from radiotherapy to diagnosis of hypothyroidism was 3.5 years (range: 0.5–9 years). Median TSH at diagnosis was 55 mIU/l (range: 5.97–100 mIU/l). TPO antibodies and antithyroglobulin antibodies were negative in all patients. All patients but one presented marked thyroid atrophy. Hypothyroidism was complicated with pericarditis in two patients.

Conclusion: Thyroid screening is mandatory for an early diagnosis of radiation-induced primary hypothyroidism and for prevention of hypothyroidism complications.