Most commonly with pulmonary valvar stenosis (not an issue at the present time) is the result when aorta valve leaflets are thickened and fused together along their separation lines (commissures). This would be congenital as mrwjd comments.
When the tissue is thickened, the leaflets become less pliable than normal and this also contributes to the obstruction. At times, the diameter of the pulmonary valve itself is small or hypoplastic, but that has been ruled out accoring to your post.
For a perspective, when the pulmonary valve is obstructed, the right ventricle must work harder to eject blood into the pulmonary artery. To compensate for this additional workload, the muscle of the right ventricle (the myocardium) gradually thickens to provide additional strength to right ventricular ejection. The increased right ventricular muscle, known as hypertrophy, is rarely a problem in itself, but instead is an indication that significant valve obstruction exists.
If your aortic valve problem is isolated (not part of occlusion of arteries or heart damage or anything), you may be looking at a congenital bicuspid aortic valve. It isn't the easiest thing to see always, but an echocardiogram should show this. Because it is an abnormal valve that doesn't open right, the leaflets can collect calcium even if your arteries and heart in general do not.
If that's what it is, no, you are not too young. You are just right! (lol)
Actually, depending on the severity of the congenital condition and the propensity of the leaves to accumulate calcium deposits, this situation can come to crisis at any age--including childhood--or never. The good news is that (a) you can, when necessary, have a surgical fix; and (b) you don't have to do it right now.
Keep a close eye on it, though. Your cardiologist (and you do need one, not a GP) may want an echo every year; make sure you get it.
Good luck.
I am a 46 year old female, I would say I jog instead of run. I have been having some palpitations so my Doctor ordered a echocardiogram and a 48 hr Holter monitor. I passed the Holter test but I too was told I had thickening of the aortic valve. I feel the same way, aren't we too young to have this? I also had an echo seven years ago and it was normal.
I am seeing a cardiologist in 3 months but I wish someone would answer your questions too! I'm wondering if possibly more people in our age group may show this but most people I know haven't even had an echocardiogram so possibly we were told something that others around our age just aren't aware of?.