title: Reversible morbidity markers in subclinical hypothyroidism.
abstract: OBJECTIVE
  Subclinical hypothyroidism (SCH) is a common clinical entity with a putative role in a wide range of disorders. The impact of SCH on mortality and markers of morbidity has been demonstrated, but studies have shown inconsistent results. Evidence regarding the effect of levothyroxine treatment on reversing morbidity markers is emerging, but the value of treatment is still unclear.
  
  
  OBJECTIVE
  The objectives of this review were to assess recent, high-quality studies evaluating the role of SCH in cardiovascular health, cognition, mood, pregnancy, anemia, and renal disease; to examine the effects of levothyroxine on reducing mortality or reversing markers of morbidity in these conditions; and to consider how new research insights may help guide clinical practice.
  
  
  METHODS
  A PubMed search was conducted (using 'subclinical hypothyroidism' [Title/Abstract] AND morbidity [MeSH Subheading] as search criteria) and was restricted to human studies published in the English language between 1990 and 2013. Subsequent searches of retrieved articles yielded further studies, which were included based on quality. Emphasis was given to large observational studies, well-conducted meta-analyses, and randomized controlled trials.
  
  
  RESULTS
  The difficulty of diagnosing SCH, particularly in the elderly, may underlie many of the conflicting results seen in the literature. Increased understanding of the at-risk patient population will result in better selection of study subjects and, likely, unequivocal results. Regardless of the current confusion, emerging evidence suggests that certain markers of morbidity are reversed by levothyroxine therapy across the disorders examined here.
  
  
  CONCLUSIONS
  Future large, well-controlled studies will not only clarify the role of SCH but also help identify patients for whom levothyroxine treatment will provide the most benefit.
authors.affiliation: Department of Medicine, Division of Endocrinology, Beth Israel Deaconess Medical Center , Boston, MA , USA.
authors.forename: James V
authors.initials: JV
authors.lastname: Hennessey
authors.forename: Ramon
authors.initials: R
authors.lastname: Espaillat
mesh_terms: D015415:Biomarkers / Q000378:metabolism*; D020249:Hormone Replacement Therapy / Q000379:methods; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy / Q000378:metabolism* / Q000401:mortality; D009017:Morbidity; D013974:Thyroxine / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D015415:Biomarkers; D013974:Thyroxine
keywords: cardiovascular morbidity; cognitive function; levothyroxine therapy; morbidity; subclinical hypothyroidism