1988 Volume 35 Issue 4 Pages 585-592
Decreased serum T3concentrations in elderly subjects and their possible relationship with the development of dementia have been indicated. To see the effects of a passive increase in the serum T3concentration, low dose T3 administration was undertaken. Forty-four subjects from 65 to 93 years of age (average 81.0±7.8) were divided into 2 groups. The grade of dementia was determined by Hasegawa's dementia rating scale (DR score). In 22 subjects, 25μg per day of T3 was administered for 4W, while the control group was given a placebo. The DR score was measured before and immediately after the study. Changes in behaviour were monitored in a double-blind fashion. The administration of T3 induced a 0.65nmol/l increase in serum T3 in 2W and 0.36nmol/l in 4W. These T3 increases were not associated with significant changes in the DR score but 7 of 22 subjects showed apparent improvement in behaviour. TSH was suppressed to less than 1mU/l in 2W and then slightly increased by the 4th week, but T4, rT3 and fT4all showed significant and progressive decreases. The DR score after T3 correlated significantly with the rT3/T4 ratio (before T3:-0.55, changes: +0.50) and also with changes in rT3 (r=0.49).
In conclusion, T3 administration to the elderly subjects was associated with behavioural improvement in some individuals, but the intellectual ability as assessed by the DR score in those with low T3 or elevated rT3 were hardly improved by passive T3 elevation.