The prevalence and the etiopathogenesis of thyroid dysfunctions in Klinefelter syndrome (KS) are still unclear. The primary aim of this study was to evaluate the pathogenetic role of hypogonadism in the thyroid disorders described in KS, with the scope to distinguish between genetic alterations or hormonal involvement. Therefore, we evaluated thyroid function in KS and in non-KS hypogonadal patients. Methods This is a case-control multicentre study from KING group: Endocrinology clinics in university-affiliated medical centres. One hundred seventy four KS, and sixty-two non-KS hypogonadal men were enrolled. The primary outcome was the prevalence of thyroid diseases in KS and in non-KS. Changes in hormonal parameters were evaluated. Exclusion criterion was secondary hypothyroidism. Analyses were performed using Student's t test. Mann-Whitney test and chi-square test. Results FT4 was significantly lower in KS vs non-KS. KS and non-KS presented similar TSH and testosterone levels. Hashimoto's thyroiditis (HT) was diagnosed in 7% of KS. Five KS developed hypothyroidism. The ratio FT3/FT4 was similar in both groups. TSH index was 1.9 in KS and 2.3 in non-KS. Adjustment for differences in age, sample size and concomitant disease in multivariate models did not alter the results. Conclusions We demonstrated in KS no etiopathogenic link to hypogonadism or change in the set point of thyrotrophic control in the altered FT4 production. These results suggest possible deiodinase impairment. The prevalence of HT in KS was similar to normal male population, showing absence of increased risk of HT associated with the XXY karyotype.

Objective: Taurodontism is a dental anomaly characterized by an enlarged pulp chamber and apycal displacement of the pulpar floor. The prevalence of taurodontism in normal population is controversial. It has been reported that taurodontism is frequently observed in Klinefelter’s patients. The purpose of this study was to assess the prevalence of taurodontism in a group of Italian Klinefelter’s patients and in a randomly selected male population of Italy and to compare the results with published data. Materials and methods: Digital panoramic radiographs of 16 Klinefelter’s patients and of 100 normal males were retrospectively studied in order to investigate the prevalence of taurodontism in these groups of patients. Results: Taurodont teeth were observed in 2 of the 16 Klinefelter’s patients (12.5%) and in 2 of 100 normal males (2.0%). Conclusions: Our results confirm the higher prevalence of taurodontism in Klinefelter’s patients compared to the normal population (12.5% vs. 2.0%). Due to the wide discrepancy of incidence of taurodontism reported in literature (0.04%-48.0% in normal population; 12.5%-88.0% in Klinefelter’s patients), we conclude that it is not possible to state which is the prevalence of taurodontism in a normal population nor among Klinefelter’s patients.

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