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Psychoneuroendocrinology. 2004 Jan;29(1):65-82.

Relationship between testosterone supplementation and insulin-like growth factor-I levels and cognition in healthy older men.

Author information

1
Department of Psychiatry and Behavioral Sciences, University of Washington Medical School, 1959 NE Pacific, Box 356560, Seattle, WA 98195, USA. cherrier@u.washington.edu

Abstract

BACKGROUND:

Our laboratory has previously reported that testosterone (T) administration to older men significantly improves cognitive function. This study examined potential changes in insulin-like growth factor (IGF) IGF-I, IGF-II and IGF-related binding proteins in response to T administration in older men and their relationship to cognitive functioning.

METHODS:

Twenty-five healthy community dwelling volunteers, ranging in age from 50-80 years were randomized to receive weekly intra-muscular (i.m.) injections of either 100 mg T enanthate or placebo (saline) for 6 weeks. Serum hormone levels and cognitive functioning was assessed at baseline and twice during treatment.

RESULTS:

Significant positive associations between IGF-I and IGF-II and spatial memory, spatial reasoning, and verbal fluency were observed after 6 weeks of T administration. Increased serum T levels from treatment were positively associated with improvement in spatial reasoning performance, whereas estradiol was associated with a decline in divided attention performance. Serum IGF-I, IGF-II and IGFBPs did not change in response to T treatment.

CONCLUSIONS:

Our results suggest that T, estradiol and IGF-I may have independent and selective effects on cognitive functioning. Positive associations between T levels and cognition are consistent with an effect of androgen treatment, whereas positive associations between IGF-I levels and cognition are reflective of a relationship between endogenous IGF-I levels and cognition.

PMID:
14575730
[Indexed for MEDLINE]

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