Thyrotropin-Axis Adaptation in Aging and Chronic Disease

Alterations in thyroid function tests in aged hospitalized patients: prevalence, aetiology and clinical outcome

“…The most common disorder is the reduction of FT3 (low T3 syndrome), whereas the reduction of FT4 is uncommon and TSH concentrations have been found normal, high or low. Other factors such as acute and chronic nonthyroidal illness and several drugs may be accompanied by changes in thyroid function tests 8,30,31 …”

“…Other factors such as acute and chronic nonthyroidal illness and several drugs may be accompanied by changes in thyroid function tests. 8,30,31 Several authors have investigated the relationship between thyroid function and morbimortality in elderly population. 9,10,12,21,[32][33][34] Some studies conducted to date, although not all, suggest that decreased TSH and increased FT4 levels are associated with an increase in mortality, whereas a mild thyroid hypofunction seems to behave as a factor that increase survival in elderly.…”

The role of Thyrotropin Releasing Hormone in aging and neurodegenerative diseases

“…These increases in TRH level off as rats approach adulthood, however with advancing age, TRH levels show a marked decrease in the hypothalamus and elsewhere in the brain (Cizza et al, 1992; Pekary et al, 1987). In addition to this, most animal studies also report a decrease in circulating T 4 levels with old age (Stan and Morris, 2005). Changes in TSH and T 3 with age however are less consistent and appear to be gender and strain specific Greeley et al (1982).…”

“…Not surprisingly, thyroid functioning and the HPT axis have been shown to undergo numerous changes with age (Stan and Morris, 2005). Thyroid function, in general, has often been studied in relation to cognition, and thereby cognitive disorders related to age.…”

“…found that increased age in female rats led to decreases in T 3 and T 4 while TSH remained unchanged (Greeley et al, 1982), however the same study found decreased T 4 and TSH mRNA in aged male rats, yet no change in serum T 3 levels. Similarly, enzymatic processing, receptor expression, and synthesis of TRH have also been demonstrated to change with age (Cizza et al, 1992; Stan and Morris, 1995). …”