Age and cognitive status dependent differences in blood steroid and thyroid hormone concentrations in intact male
Jovana Maliković1, Daniel Daba Feyissa1, Predrag Kalaba1
1Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria.
Background:
Age-dependent alterations of hormonal states have been considered to be involved in age related decline of cognitive abilities. Most of the studies in animal models are based on hormonal substitution in adrenal- and/or gonadectomized rodents or infusion of steroid hormones in intact rats. Moreover, the manipulations have been done timely, closely related to test procedures, thus reflecting short-term hormonal mechanisms in the regulation of learning and memory. Here we studied whether more general states of steroid and thyroid hormone profiles, independent from acute experiences, may possibly reflect long-term learning capacity. A large cohort of aged (17-18 months) intact male rats were tested in a spatial hole-board learning task and a subset of inferior and superior learners was included into the analysis. Young male adult rats (16 weeks of age) were also tested. Four to 8 weeks after testing blood plasma samples were taken and hormone concentrations of a variety of steroid hormones were measured by gas chromatography-tandem mass spectrometry or radioimmunoassay (17β-estradiol, thyroid hormones).
Results:
Aged good learners were similar to young rats in the behavioral task. Aged poor learners but not good learners showed higher levels of triiodothyronine (T3) as compared to young rats. Aged good learners had higher levels of thyroid stimulating hormone (TSH) than aged poor learning and young rats. Both aged good and poor learners showed significantly reduced levels of testosterone (T), 4-androstenedione (4A), androstanediol-3α,17β (AD), dihydrotestosterone (DHT), 17-hydroxyprogesterone (17OHP), higher levels of progesterone (Prog) and similar levels of 17β-estradiol (E2) as compared to young rats. The learning, but not the memory indices of all rats were significantly and positively correlated with levels of dihydrotestosterone, androstanediol-3α,17β and thyroxine (T4), when the impacts of age and cognitive division were eliminated by partial correlation analyses.
Conclusion:
The correlation of hormone concentrations of individuals with individual behavior revealed a possible specific role of these androgen and thyroid hormones in a state of general preparedness to learn.
Insights
General hormone profiles, not acute changes, may influence long-term learning capacity. Androgen and thyroid hormones appear crucial for a general readiness to learn in aged rats.
Area of Science:
- Neuroscience
- Endocrinology
- Aging Research
Background:
- Age-related cognitive decline is linked to hormonal changes.
- Previous studies often used acute hormonal manipulations, limiting understanding of long-term effects.
- This study investigates general, long-term hormone profiles in relation to learning capacity in aged rats.
Purpose of the Study:
- To determine if general steroid and thyroid hormone profiles, independent of acute interventions, correlate with long-term learning capacity in aged rats.
- To compare hormone profiles and learning abilities between young and aged rats, and between aged good and poor learners.
Main Methods:
- Aged (17-18 months) and young (16 weeks) male rats were tested on a spatial hole-board learning task.
- Rats were categorized into good and poor learners.
- Blood plasma hormone concentrations (steroid and thyroid hormones) were measured 4-8 weeks post-testing using GC-MS and RIA.
Main Results:
- Aged good learners performed similarly to young rats.
- Aged poor learners exhibited higher triiodothyronine (T3) levels than young rats.
- Reduced testosterone (T) and related androgens, alongside higher progesterone, were observed in aged rats (both good and poor learners) compared to young rats.
- Learning capacity positively correlated with dihydrotestosterone (DHT), androstanediol-3α,17β (AD), and thyroxine (T4) levels after controlling for age and learning ability.
Conclusions:
- Specific androgen and thyroid hormone profiles are associated with an individual's general preparedness to learn.
- These findings suggest a role for baseline hormone levels in long-term cognitive function during aging.
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