Extremely sudden shed after gym session!!

Creatine spike in DHT levels, are you using a keto shampoo? I found pre workouts to be more harsh than standard 5 gram creatine.

Yes im using keto shampoo but did not shower straight after. If a spike in DHT was caused surely the DHT wouldn't cause the hair to fall out instantly? In my understanding the DHT first miniaturises the hair before it falls out

Wrong I had the same case when I took pre work out my scalp was tingling and itching etc.

I would be very surprised if it's got to do with DHT levels to account for an acute shed as you describe. There are a lot of other hormones at play while working out, such as cortisol, which could also lead to hair loss. Hard to isolate the cause, but I wouldn't worry terribly much, try to keep stress down and lower intensity of weight lifting.

I suspected that it was maybe telogen efluvium. Is it possible for heavy weightlifting and possibly irregular breathing to cause some stress in the scalp causing temporary and sudden hairloss?

It has to be the pre work out, when I used c4 it caused me to thin out.

No idea. I am not aware of any data about that. I do know that chronic stress can lead to hair loss, the telogen effluvium kind, but weightlifting and aerobic exercise spike cortisol levels -- stress hormone -- but this is only temporary and shouldn't lead to a spontaneous amount of hair coming out. But there is normal hair loss per day, did you experience more than 100 hairs lost in that single instance? If so, then you really should see a doctor as soon as you can, that is not normal at all, especially just in response to weight training.

Unfortunately my doctor and dermatologist dont know much about hairloss. If the hairs that did come out had a little white bud on the end is that a good sign?

Think I remember that being indicative of telogen effluvium. From drugs.com (http://www.drugs.com/health-guide/te...effluvium.html)So it's a good sign, because telogen effluvium isn't something that usually leads to permanent loss, but will grow back within 6-9 months. A rather long wait, I know, I actually experienced the same type of hair loss recently and am still waiting for the hairs to grow back after 5 months.

Have you tried looking for a different dermatologist?

Had a similar intensity workout a few hours ago without preworkout and have not had any itching or shedding. Just wish i knew what ingredients were causing it so i can find a preworkout that is safe

I'm not sure what stage you are at with your bodybuilding, but from my experience pre-workout supplements are not worth the cost or risk to your hair and general health.
I have been making very good progress with only a solid meal and a little caffeine as my pre-workout. Staying consistent with your routines is the best way to be prepared for the next workout.
Most of the workout supplements on the market are created in a complete chemical sh*t-storm of ingredients that you need to be a chemist to identify. I gave them up completely and have saved myself the money and worry about risking further hair-loss from weird chemicals.
I can honestly say that none of the pre-workout supplements I used to take did anything more than a caffeine drink and a good warm up routine can do. You don't need that stuff to make gains.

Thanks for the advice! Im 21 now and iv been drinking preworkout 4 times a week since i was 16. So hopefully by quitting that and continuing propecia ill save my hair

@Karlton whats your opinion on whey protein and protein shakes in general in terms of hairloss?

I have been on finasteride for over 12 years, and I have used whey protein off an on within that time. Whey is a convenient, inexpensive means of getting a little extra protein into your diet. It also tastes better than the other types of protein shakes out there.
I don't believe it's ever had a negative effect on my hair, but again I take finasteride so it may have been the medication that was protecting my hair. I have read that some doctors are saying that whey protein isolates can cause spikes in your DHT and subsequent hair shedding, but I'm not sure if there is any hard evidence there. I will have a whey protein shake once in a while, but I alternate with other types of protein shakes like soy, rice, grass, sprout. I like some variety, and I try not to overdo it with any one type of protein. I also try to stick with shakes that have natural and organic ingredients. I am amazed at the list of chemical ingredients in some of these bodybuilding supplements these days. It's scary to think how quickly people will empty their wallets, and fill there bodies with chemicals they can't even pronounce.
Now that I have been lifting for a few years, I have realized that the best and most reliable way to get the protein you need is through real food. I try to spend my time and money keeping lots of good, wholesome food and drinks in my fridge. I do like a shake for breakfast, and post-workout, simply for the convenience. Good luck with your gains!