Thyroid dysfunctions and metabolic changes in centenarians: consequence or cause of longevity?

Overt as well as subclinical thyroid dysfunctions are associated with metabolic changes that affect cardiovascular risk. In centenarians low T3 but normal TSH levels have been described that resemble those described in patients with a severe illness (low-T3-syndrome). We investigated 101 out of total 618 centenarians (age 100–105; 90 women and 11 men) living in Berlin. The following data were assessed: clinical data (presence or history of cardiovascular disease, family history, Mini Mental Status Test, physical examination, BMI, blood pressure) and laboratory parameters (TSH, free T4, T3, thyroid antibodies, cholesterol, HDL-cholesterol, LDL-cholesterol, triglyceride, ghrelin, bound and free leptin, leptin receptor, adiponectin). The clinical data were as follows: Body mass index was 20.8±3.4 Kg/m²; Mini Mental Status Test: 15,1 + 9,7 (median 18,5; range 0–28); myocardial infarction in 4/101 (3.9%); stroke in 12/101 (11,9%); arterial hypertension in 36/101 (35,6%); mild heart failure in 50/101 (49,5%); diabetes in 27/101 (26,7%) with 14/101 (13,9%) on diet, 8/101 (7,9%) on oral medication and only 5/101 (4, 95%) on insulin therapy. Laboratory parameters were as follows: TSH 1,22 + 1,35µU/ml; free T4 1,12 + 0,29 ng/dl; T3 0,64 + 0,19 ng/ml; thyroid receptor antibodies negative; TPO antibodies and/or TG antibodies positive 4/60 (6,7%); total cholesterol 191,2 + 42,5mg/dl; HDL-cholesterol 53,3 + 16,6mg/dl; LDL-cholesterol 127,1 + 34,7mg/dl. Overt hyperthyroidism was present in 2/101 (2%); a decreased TSH, in 19/101 (18,8%). However, 12 of the latter patients had also decreased and only 9 normal T3. Hypothyroidism was present in 2/101 (2%).

The data suggest that longevity is associated with a low body weight (very low BMI) and a decreased metabolic rate as the cause of a highly reduced cardiovascular risk. Low T3-syndrom may be the consequence rather than the cause of these conditions in centenarians. Accordingly a very low TSH in about 20% of centenarians may be due to an altered central regulation of thyroid rather than hyperthyroid conditions.