Sudden bout of fatigue

I'm a 76 years old male and yesterday after taking a class in college, I felt extremelly fatigued like if I wanted to go home to lay down. I took my blood pressure at home and it was 130/72 with a pulse of 88. I had no shortness of breath and no chest pain, only some discomfort in my neck and upper back (I have arthritis in my neck). In March of this year, I had an aneurysm repaired in my ascending aorta and had a normal recovery from the surgery, to the point that I was able to play tennis. My concern is that before this episode, I did not do any strenuous physical or mental work like other times when I have felt this fatigued.

Have you ever had your T level checked I recently went thru the same thing and I'm only 48 yrs old having low T level can cause heart problems and can have effects on blood sugar levels and how your body uses insulin Oh and libdo which I was still fine in that area.Low T levels in men can also give you the beer belly.Something to think about hope this helps.