Hello,
Thank you for asking the query :
Low testosterone levels could cause some of these symptoms especially the sex relaxed ones and the muscle mass loss. However it will not explain the decrease in exercise capacity, sleep problems, weight gain and depression.
A normal testosterone level definitely indicates the levels are normal for you. So we should focus elsewhere for any derangement. Since you are having this amount of symptoms, a thorough clinical examination followed by a set of lab tests is recommended. The following blood tests ( if not done earlier ) are recommended.
· Hb and Complete blood cell (CBC) count
· Thyroid-stimulating hormone (TSH)
· Vitamin B-12 levels
· Electrolytes, including calcium, phosphate, and magnesium levels
· Liver function tests (LFT)
· Blood urea nitrogen (BUN) and creatinine
· Dexamethasone suppression test
· Cosyntropin (ACTH) stimulation test
This will give an idea on what is the possible underlying pathology for the above mentioned symptoms.
Also please note: Depression itself is potent enough to cause all the symptoms mentioned. Since you are on treatment it needs to optimised in discussion with your Doctor. Lack of sexual desire is a possible side effect of anti-depressive medications.
Regarding exercise , you need to stay physically active even though you feel the endurance level is low. Otherwise chances are that your aerobic and anerobiccapacity will decrease over the time. Moreover the endorphins released during exercise will elevated you mood can help in insomnia.
Hope this helps. Please feel free to ask followup questions. Thank you.