Muscle cramps early in marathon

Question
Hi,
I am 29 and recently finished my first marathon in Baltimore. I felt that I was well trained. I had run 2 20 mile runs, 1 21 mile run, and I think even 3 18 mile runs. Only developed cramps during the 21 mile run-starting about mile 17 and not severe-and at the very end of one 20 mile run. The 21 mile run was incredibly humid and I attributed the cramps to excessive sweating. In the 20 mile run,I got cramps at the end, and it was quite fast for me so I felt it was just muscle fatigue and did not intend to run my marathon at that pace.

Unfortunately, on the day of the marathon, I started to get cramps in my calfs on mile 10. I really have no idea why.

It was slightly warm (upper 60's to 70's) and humid during the beginning-seemingly compounded by body heat and crowding during the first 5-6 uphill miles but progressively got cooler due to a cold front.

I was drinking gatorade at all stations. I feel I finished well-hydrated. Only different thing I did pre-race was drink some gatorade that I had carried to the race.

Somehow I managed to run 16.2 more miles. I had to slow my pace and focus on not freaking out.

I am just very frustrated because I do not understand why this happened and how to prevent it again. I think it is compounded by the fact that I am a doctor (pulmonary and critical care fellow) and feel that I should be able to figure this out but I really can't. And I know that muscle cramps in endurance sports are not well understood.

One more possibility, I did not generally have much incline in my long runs though I did not infrequently run hills on regular runs.

Thank you for your help,
Beth

Answer
Hi Beth
Considering your position as a Medical Doctor and the need to get a very in depth history of a  situation to make a very focused and informed decision,is it possible to discuss this situation with you over the phone.I'm in the same business and need to ask you a number of questions which is hard to do in email?I can be reached here in Albuquerque at 505 271 5909 from 6am om.

Looking forward to
your response

John