Blood micronutrient and thyroid hormone concentrations in the oldest-old

Several micronutrients are involved in thyroid hormone metabolism, but it i s unclear whether their marginal deficits may contribute to the alterations in thyroid function observed in extreme aging. The relationships among blo od concentrations of thyroid hormones and selenium, zinc, retinol, and alph a-tocopherol were studied in 44 healthy Northern Italian oldest-old subject s (age range, 90-107 yr), selected by the criteria of the SENIEUR protocol. Control groups included 44 healthy adult (age range, 20-65 yr) and 44 SENI EUR elderly (age range, 69-89 yr) subjects. Oldest-old subjects had higher TSH (P < 0.01) and lower free T-3 (FT3)/free T-4 (FT4) ratio, zinc, and sel enium serum values (P < 0.001) than adult and elderly control subjects. No significant difference was found for plasma retinol and alpha-tocopherol va lues. The associations between micronutrients and thyroid hormones were eva luated by multivariate analysis. In oldest-old subjects, plasma retinol was negatively associated with FT4 (P = 0.019) and TSH serum levels (P = 0.040 ), whereas serum zinc was positively associated with serum FT3 (P = 0.010) and FT3/FT4 ratio (P = 0.011). In younger subjects, no significant associat ion was found among thyroid variables and micronutrients. In conclusion, bl ood levels of specific micronutrients are associated with serum iodothyroni ne levels in extreme aging.