CONTEXT: Although the negative impact of subclinical hypothyroidism (sHT) in 
terms of cardiovascular risk in young adults is mostly acknowledged it remains 
to be established in the elderly, especially in the oldest old.
EVIDENCE ACQUISITION: We searched Medline for reports published with the 
following search words: hypothyroidism, sHT, ageing, elderly, L-thyroxin, 
thyroid, guidelines, treatment, quality of life, cardiovascular risk, heart 
failure (HF), ischemic heart disease (IHD), endothelial dysfunction. The search 
was restricted to reports published in English since 1980, but some reports 
published before 1980 were also incorporated. We supplemented the search with 
records from personal files and references of relevant articles and textbooks. 
Parameters analyzed included epidemiology of sHT and thyroid failure the effect 
of thyroid hormone on ageing process and cardiovascular function as well as the 
potential benefits of L-thyroxin therapy on quality of life, HF progression and 
events.
EVIDENCE SYNTHESIS: TSH levels increase with age, even in older patients without 
thyroid disease, in whom higher TSH value might favor longevity; better quality 
of life and lower IHD mortality in the oldest old population has been reported 
yet. However, at odds with the relationship between sHT and IHD risk and 
mortality, which shows a clear age dependent feature, vanishing in the last 
decades of life, the detrimental effect of sHT on HF progression and events 
remains evident also in older patients, although no data are available in the 
oldest old population.
CONCLUSIONS: The lack of specific randomized trials enrolling either old or very 
old subjects, aimed at evaluate the efficacy of hormonal replacement on overall 
survival and cardiovascular risk reduction along with the negative effects of 
possible over-treatment, makes the decision to treat older people a still 
unresolved clinical challenge. Moreover, the possibility that restoring 
euthyroidism may be harmful in the elderly should be always taken into account.