Endocrine Abstracts

Introduction: Familial Adenomatous Polyposis (FAP) syndrome is an autosomal dominant disorder associated with a high risk of multiple intestinal and extraintestinal cancers. They develop hundreds or thousands of adenomas in the rectum and colon during the second decade of life that. If they are not identified and treated, almost all patients develop colorectal cancer (CRC) and die by the age of 40-50 years. Thyroid carcinoma is a FAP manifestation with an unknown reported higher risk with an approximate prevalence of 1-2%. We sought to define the prevalence of t thyroid pathology, defined as autoimmunity, nodularity, and carcinoma.

Materials and methods: Prospective study, selecting 17 living patients diagnosed and registered with APC mutations under follow-up from the Digestive Department of the Hospital Universitario de Navarra (HUN) with current or past follow-up in the Endocrinology Department. Radiological tests, clinical, and analytical variables were analyzed.

Results: The study population included 12 men (64.7%) and 5 women (35.3%), with a mean age of 47 years. The median age at diagnosis of FAP was 28 years, with a mean follow-up time of 16 years. All patients underwent thyroid ultrasound examination and blood tests with the determination of thyroid autoimmunity. The prevalence of nodular pathology was 58.8% (10/17), of which 7 had single nodules and 3 had multinodular goiters. Of the 10 patients with nodular pathology, 5 had nodules >1 cm (29.4% of the total sample). Of these, 4 had indications for cytologic study. The result of the cytologic study was Bethesda II in 3 cases and Bethesda IV in one, so surgical treatment was necessary. The anatomopathological study was follicular adenoma. No malignancy was found in the sample. The overall prevalence of autoimmunity is 31.25% (5/16). Of the 5 patients with thyroid autoimmunity: 2 present thyroid peroxidase antibodies (40%), 2 thyroglobulin antibodies (40%), and 1 patient both (20%).

Conclusion: The prevalence of thyroid nodularity in the sample of patients with FAP is above that described in the general population. Probably the small number of patients in the sample has conditioned the non-detection of thyroid carcinoma.