High heart rate on minimal exertion

[SMW65]

I have exercised my whole life, did 2 half marathons and one full, one sprint tri, play tennis, etc.
Since July (when I started running again) my heart rate starts out manageable, then after 5-10 minutes my heart rate continues to climb sometimes reaching 190 if I don't slow down (which I have to because I'm so breathless). I am jogging a 12 min. mile now and try to slow to control my HR but can't . I have a garmin 305 that charts it all out. Some days are better than others. I had a treadmill test per my primary that was normal although they did say that my heart looked like someone who had never worked out before (which I know is not true). Also, echo normal.
Went to my endorcrinologist (I have PCOS, but not overweight). My cortisol was slightly elevated, norepinephrine was too. Low free testosterone and slightly hypothyroid (borderline).
Now he wants me to see an EP because of the heart rate. It's like my body wants to go and my heart can't keep up. Even walking up the stairs my heart rate jumps to 130. Help!

[SMW65]

I guess with biking I push hard and my hr gets high (over180), but it seems to match my exertion. When I slow down to a conversational pace I'm around 160 which seems light....doesn't seem right to me either.

[Jerry_NJ]

I don't know about athletic swimming, I'm can just get my self to shore if it isn't over a 100 yards, but I too think the respiratory load for biking and running should have similar affect on you HR.  I have no idea why there is a difference (assuming you believe you are working as hard or harder on the bike).  Perhaps the jarring of the feet on the pavement, contrasted with a rolling wheel, has some affect.  Again I don't know, just guessing.  If the "flutter" is at the same time as the high HR that could be the driver, e.g., an artial flutter or fibrillation can force the HR up, especially under load.  I'd double check the difference between running and biking, it is a strange result to my mind.    

[SMW65]

Thanks for your reply. Yes, I do occasionally notice a flutter or skipped beat... Usually as I'm cooling down. I also don't have this when I swim or bike which doesn't seem logical to me.
I can be running at a slow pace, flat or downhill and my heart rate will continue to rise.

[Jerry_NJ]

You didn't mention any irregular (skipped/extra/missing) rhythm problems so I assume none are noted.

You said "started running again" but mention 12 minute miles, which unless on an upgrade should be a light workout from what you tell us of your past athletic activities.  I think a check-up with an EP would be a good idea.

I agree your HR is too high for the level of workout and assumed physical condition as you describe it.