Thank you for taking the time to share on our forum.
Iron deficiency is a common, but sometimes debilitating problem. This can lead to anemia, and symptoms of shortness of breath and fatigue, as you are feeling. An EKG is a common test that doctors often use to evaluate symptoms similar to yours. This is a test that records the electrical impulse that travels through your heart and corrdinates its beating. The EKG consists of several different "waves" and "segments" which can describe many different anatomical features, and pathologic conditions effecting the heart.
The "ST junction" you are referring to is the part of the EKG that is between the QRS (which corresponds to the left ventricle contracting - or "depolarizing") and the T wave (which corresponds to it recharging - or "repolarizing"). The ST segment may be depresed in a variety of conditions, including a lack of blood flow to certain parts of the heart - or "ischemia". However, the upsloping nature of your ST segment depressions is usually reassuring, but still can indicate ischemia in the right context. Although there are other reasons to have upsloping ST segment depressions on the EKG (such as a normal variant), your doctor is concerned enough that this may indicate ischemia, and is thus ordering a stress test to figure this out.
ST segments can become more severe during times of stress on your body, such as iron deficiency. However, this is not diagnostic for iron deficiency, and your doctor should look into this more definitively with laboratory testing if they are concerned.
I truly value your time and hope you find this information helpful.
Very best wishes into the future.