ESPE Abstracts

Objectives: Prader-Willi syndrome (PWS) is a complex multisystem disorder due to loss of expression of paternally derived genes in the PWS critical region on chromosome 15q11-q13. The majority of the cases are due to the deletion of this region (del15), while 20–30% are caused by a maternal uniparental disomy of chromosome 15 (UPD15). The clinical picture is characterized by neonatal hypotonia and feeding difficulties in early infancy, early development of hyperphagia with progressive development of severe obesity (if uncontrolled), short stature, behavioural problems, cognitive impairment, psychiatric illness, and multiple endocrine abnormalities. Disturbances in the hypothalamic-pituitary-thyroid axis are observed with variable frequency in PWS. Hypothyroidism is the most frequent alteration, and may be of central or peripheral origin. Other thyroid abnormalities in PWS subjects are rarely reported, including congenital hypothyroidism caused by an ectopic sublingual thyroid gland and fetal goiter. Because data on the ultrasonographic examination of the thyroid gland in PWS subjects are not currently available, this preliminary study aims to evaluate the thyroid morphology and function in transition individuals and young adults with PWS.

Methods: Twenty subjects with genetically confirmed PWS [15 patients with del15 and 5 individuals with UPD15, 12 females, aged 30.6±5.9 year (mean+S.D.) (range 18.0–39.0 year), Body Mass Index (kg/m²) 46.7±8.8 (range 35.8–63.5] were studied. Thyroid function tests, including antithyroid antibodies, and thyroid ultrasonography (TUS) were performed in all subjects.

Results: Eighteen PWS subjects were euthyroid, while 1 female had central hypothyroidism and 1 female showed an overt hyperthyroidism. Antithyroid antibodies were negative in all subjects. TUS demonstrated a mild hypoechogenicity in 6 cases (30%) and a hyperechogenic pattern in 1 female. Six PWS had nodules with a diameter >5 mm (30%); 2 females had a single nodule, while 2 nodules were found in 3 females and 1 male. In 2 patients there were parenchymal microcalcification. Thyroid vascularization was reduced in 5 subjects.

Conclusions: Our results seem to demonstrate that alterations in thyroid structure can frequently be observed in patients with PWS. In this light, screening for altered thyroid morphology should be a routine element of care for individuals with PWS.