Heritability of thyroid peroxidase autoantibody levels in type 1 diabetes:evidence from discordant twin pairs

Aims/hypothesis The discordance status of (autoimmune) type 1 diabetes within monozygotic twin pairs points to the importance of environmental factors. The aim of this study was to investigate whether the environmental events causing type 1 diabetes influence thyroid autoimmunity. Methods Monozygotic and dizygotic twins discordant for type 1 diabetes from the UK and USA were tested for thyroid peroxidase autoantibodies (TPOA) by radioimmunoassay. Using quantitative genetic model fitting of a liability-threshold model we estimated the contribution of genetic (heritability) and environmental factors to TPOA. Results TPOA positivity was higher in females than in males in both cohorts and was associated with later age at diagnosis in the UK and combined cohorts (p 0.2 in all groups). The best-fitting models showed heritability (95% CI) estimates for TPOA of 63% (37%, 80%) for the UK and 80% (51%, 92%) for US twins, while the best-fitting meta-analysis model of the two twin cohorts combined included additive genetic and unique environmental factors with a heritability estimate of 69% (50%, 82%). Conclusions/interpretation Risk of thyroid autoimmunity, defined by TPOA, in the context of autoimmune diabetes is, substantially, genetically determined in discordant twin pairs. Environmental factors leading to type 1 diabetes were not the same as those involved with thyroid autoimmunity. It follows that it is as important to investigate for thyroid autoimmunity in relatives of type 1 diabetes patients as it is in the patients themselves

Spectrally resolved wave-mixing between near- and far-infrared pulses in gas

We investigate the nonlinear wave-mixing in gases between intense, short optical pulses and long-wavelength fields (mid infrared and terahertz). We show numerically that the beating between the sum- and difference-frequency generation components can be isolated in the spectrogram of the interaction, and can be used to sample the electric field oscillations of the long-wavelength pulses. This, in turn, could be employed as a possible characterization method that provides information on the real electric field amplitude. Our numerical model is supported by spectrally resolved measurements of the four-wave mixing signals obtained from the interaction of intense, single-cycle terahertz fields (λ > 15 μm) and optical pulses (λ ≃ 800 nm, 50 fs duration) in air. © IOP Publishing and Deutsche Physikalische Gesellschaft