If Cabergoline is controlling my prolactinoma, why is my testosterone low?

[MedicalHelpUser2018]

I was put on Cabergoline to treat a pituitary micoradenoma. It worked great; my prolactin level went way down and my testosterone shot up. I felt great!

I'm about to have my 6 month follow up, and I just had my blood tested. My prolactin is down, but my testosterone is now down to pre-treatment levels. Explanation? I am going to ask my endocrinologist to put me on testosterone.

Pre-treatment:
Prolactin: 37.2 ug/L
Testosterone: 12.1 nmo/L

2 months after starting Cabergoline:
Prolactin: 18.0 ug/L
Testosterone: 20.9 nmo/L

6 months:
Prolactin: 12.3 ug/L
Testosterone: 12.2 nmo/L

reference ranges:
Prolactin: 3.8-20.6 ug/L
Testosterone: 8.4-28.8 nmo/L

All blood testing was done first thing in the morning.

I am male, 37 y/o, 15% bodyfat, and I exercise 6 days a week, sometimes twice a day.
I have lost most interest in sex. For years I suffered from erectile dysfunction. I also recently had my body composition scanned in a DEXA scanner which found that I am osteopenic. This is quite serious as my entire thoracic spine was fused and metal implants put in to treat Scheuermann's Disease (kyphosis). I am showing degeneration at several levels of the fusion. I have also been diagnosed with idiopathic anemia (RBC = 3.99 10*12/L, Hemoglobin = 118 g/L, Hematocrit = 0.35 L/L, Ferritin = 85 ug/L). I have developed melasma on my forehead which my dermatologist said could be related (pregnant women often get melasma). I also have atypical patterns of hair loss/thinning though there is no real baldness in my family.