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Since the advent of biochemical screening for congenital hypothyroidism, the majority of monozygotic twins reported with thyroid dysgenesis have been discordant, and most were missed on neonatal screening, presumably due to fetal blood mixing. We hypothesized that there may be bias leading to preferential reporting of discordant twins and/or of false negative screening results. Therefore, we performed a systematic search for twins in two congenital hypothyroidism screening centers, Quebec and Brussels, that use a primary TSH approach. In Quebec, 10 pairs of twins were identified, all discordant for congenital hypothyroidism due to thyroid dysgenesis (4 monozygotic and 4 dizygotic pairs) and dyshormonogenesis (2 dizygotic pairs). The 6 pairs identified in the Brussels database were also all discordant for congenital hypothyroidism due to thyroid dysgenesis (1 monozygotic and 3 dizygotic pairs) and dyshormonogenesis (2 dizygotic pairs). The median increase in TSH between screening and diagnosis was 7-fold in the monozygotic twins vs. 2-fold in matched singletons (P = 0.02), suggesting fetal blood mixing between the twins. In summary, discordance for thyroid dysgenesis is the rule in monozygotic twins, and fetal blood mixing may result in delayed or missed diagnoses. We therefore conclude that 1) a second sample for congenital hypothyroidism screening at 14 d of age should be considered for all same-sex twins; and 2) thyroid dysgenesis generally results from epigenetic phenomena, early somatic mutations, or postzygotic stochastic events.

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Despite the dysfunctional StAR, pregnancy is possible under the proper therapeutic strategy.

SUMMARY:Our prospective survey of 50 ataxic patients confirms the previous finding of frequent clinical or chemical diabetes in Friedreich's ataxia. Eighteen percent of our typical cases have clinical diabetes and 40% at least an abnormal glucose tolerance curve. However, this finding does not appear to be specific to that form of ataxia. Furthermore, we have shown that most patients with ataxia have normal or low fasting insulin levels, but a hyperinsulinic response to a glucose load.