ESPE Abstracts

Background: Allan-Herndon-Dudley syndrome (AHDS) is an x-linked mental retardation syndrome characterized by severe psychomotor retardation and pathognomonic thyroid parameters. Defects in monocarboxylate transporter 8 (MCT8), which facilitates thyroid hormone (TH) uptake and efflux across plasma membranes, have been linked to this disease. The incidence of undescended testes was reported to be 8% by Schwartz et al. On the other hand, we had the impression that cryptorchidism may be more frequent in patients with a severer phenotype.

Objective and hypotheses: To determine whether the prevalence of cryptorchidism is higher in severely affected AHDS patients than previously reported.

Method: A retrospective chart review of six AHDS patients seen at an academic medical center was performed. All patients demonstrated the severe phenotype; neither one could speak nor walk. Evaluation of the hypothalamic–pituitary–gonadal (HPG) axis was performed when possible.

Results: The ages of the patients ranged from 3 years 3 months to 12 years 2 months (median: 6 years 8 months, mean: 7 years 0 months) on their last visit. Four were prepubertal, two were at the early stages of puberty. Due to undescended testes, unilateral or bilateral orchidopexy had been performed in one and three patients respectively. The contralateral testis was retractile in the patient who underwent unilateral orchidopexy. The remaining two also had retractile testes. Testis volume was 1–2 ml in all patients.

Conclusion: Two thirds of the patients with severe AHDS manifested cryptorchidism, suggesting that sufficient TH transport may be necessary for testicular descent. The lower incidence in the initial study may be due to the large fraction of mildly affected patients in the cohort. Early detection is essential to avoid various complications that stem from this condition.