Copy number variation in common disease

Thyroid status and functional and cognitive status at baseline and survival after 3 years of follow-up: the OCTABAIX study

OBJECTIVE

Subclinical thyroid disorders are common in older individuals. Health risks associated with subclinical hypothyroidism in older adults are unclear. The aim of the study is to evaluate whether thyroid status in elderly subjects correlates with physical and cognitive function at baseline and with 3-year mortality.

DESIGN

A population-based, prospective cohort of the OCTABAIX study (307 inhabitants aged 85 years at baseline).

METHODS

Chronic drug prescription, functional status (Barthel and Lawton indices) and cognitive status according to the Spanish version of the Mini-Mental State Examination were recorded. Quality of life was assessed using the visual analogue scale of the quality of life test. Concentrations of TSH and thyroxine were measured. Participants were classified in accordance with clinical categories of thyroid function.

RESULTS

Twenty (6.5%) individuals had subclinical hypothyroidism and five (1.6%) had subclinical hyperthyroidism. Compared with euthyroid subjects (n=280; 91.8%), subclinical hypo- and hyperthyroidism subjects were not significantly associated with poor physical or cognitive function at baseline. Fifty-one (15.1%) subjects died during the 36 months of follow-up. TSH values and subclinical hypo- and hyperthyroidism were not associated with an increased overall mortality risk (hazard ratio (HR) 1.086, 95% CI 0.987-1.196 and HR 0.905, 95% CI 0.902-1.053 respectively).

CONCLUSIONS

This study does not support the association of TSH or thyroid disorders with physical or cognitive function at baseline or with 3-year mortality in the oldest old subjects.

Immunogenetic mechanisms leading to thyroid autoimmunity: recent advances in identifying susceptibility genes and regions

The autoimmune thyroid diseases (AITD) include Graves’ disease (GD) and Hashimoto’s thyroiditis (HT), which are characterised by a breakdown in immune tolerance to thyroid antigens. Unravelling the genetic architecture of AITD is vital to better understanding of AITD pathogenesis, required to advance therapeutic options in both disease management and prevention. The early whole-genome linkage and candidate gene association studies provided the first evidence that the HLA region and CTLA-4 represented AITD risk loci. Recent improvements in; high throughput genotyping technologies, collection of larger disease cohorts and cataloguing of genome-scale variation have facilitated genome-wide association studies and more thorough screening of candidate gene regions. This has allowed identification of many novel AITD risk genes and more detailed association mapping. The growing number of confirmed AITD susceptibility loci, implicates a number of putative disease mechanisms most of which are tightly linked with aspects of immune system function. The unprecedented advances in genetic study will allow future studies to identify further novel disease risk genes and to identify aetiological variants within specific gene regions, which will undoubtedly lead to a better understanding of AITD patho-physiology.