Subclinical hypothyroidism in community-dwelling older people: consequences and treatment outcomes

Abstract

The thyroid gland plays a crucial role in regulating nearly all bodily processes. A particular state of thyroid function, dubbed subclinical hypothyroidism (with high thyroid-stimulating hormone [TSH] and normal free thyroid hormone [fT4] in blood tests), becomes more prevalent with advancing age and it is unclear how this condition should be interpreted in community-dwelling older people (arbitrarily 65 years and older). Whether or not the condition is associated with negative health consequences, and whether treatment with levothyroxine (artificial thyroid hormone) is warranted, are subjects of decades-long debate. This thesis aims to identify whether subclinical hypothyroidism is associated with a range of relevant outcomes, and whether levothyroxine treatment leads to benefits, in community-dwelling older persons. The results in this thesis demonstrate that subclinical hypothyroidism is not associated with clinically (e.g. physical and cognitive function, mood or mortality risk) or biologically (e.g. thyroid antibodies or anaemia) relevant outcomes. Levothyroxine treatment does not provide benefits. These results suggest that subclinical hypothyroidism in older people is a strictly biochemical diagnosis, they support more conservative diagnostic approaches and do not support routine treatment with levothyroxine. More research is needed before extrapolating to more specific subgroups and to assess whether international guidelines should be updated.</p