Why older rats don't get as fast-hearted from thyroid hormone
Effects of thyroid hormone on beta-adrenergic responsiveness of aging cardiovascular systems.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Thyroid hormone makes the heart beat faster in young rats, but not as much in old rats. Giving thyroid hormone to old rats helps their hearts respond a little better to a stress chemical, but not because they grow more receptors.
Surprising Findings
T3 increased beta-receptor density equally in young and old rats, yet cardiovascular responses remained weaker in the aged.
It contradicts the assumption that age-related blunting is due to fewer receptors. The study shows receptor count isn't the issue—something downstream is broken.
Practical Takeaways
If you're over 60 and have thyroid issues, don't assume more hormone will fix heart rate or blood vessel problems the way it does in younger people.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Thyroid hormone makes the heart beat faster in young rats, but not as much in old rats. Giving thyroid hormone to old rats helps their hearts respond a little better to a stress chemical, but not because they grow more receptors.
Surprising Findings
T3 increased beta-receptor density equally in young and old rats, yet cardiovascular responses remained weaker in the aged.
It contradicts the assumption that age-related blunting is due to fewer receptors. The study shows receptor count isn't the issue—something downstream is broken.
Practical Takeaways
If you're over 60 and have thyroid issues, don't assume more hormone will fix heart rate or blood vessel problems the way it does in younger people.
Publication
Journal
The American journal of physiology
Year
1987
Authors
G. Tsujimoto, K. Hashimoto, B. Hoffman
Related Content
Claims (4)
When your body has too much thyroid hormone, it makes your heart beat faster and makes you sweat more—even when you're not exercising or stressed out.
In older rats, giving them a thyroid hormone helps their blood vessels respond better to a chemical that normally makes them relax — but only partly. This suggests that as rats age, their thyroid hormones and blood vessel reactions become less connected.
As rats get older, their hearts don't respond as well to a hormone that makes the heart beat faster, but giving them a thyroid hormone helps a little bit — showing that aging and thyroid function work together to affect heart rate.
Giving thyroid hormone makes the same increase in certain heart receptors in both young and old rats, but that change doesn’t explain why older rats’ hearts don’t respond the same way to adrenaline as younger ones.