How does testosterone therapy work? What are the steps used to get to treatment?

I'm getting a blood test next month and I'm wondering if all blood tests check for testosterone levels? And if most blood tests don't check for testosterone levels, what can I do or what do I have to do in order to make sure that my testosterone levels are found out?

I am certain, without a doubt that I have hypogonadism, (probably primary hypogonadism), and I want to know if blood tests check for testosterone levels so that I can hopefully get referred to a urologist/endocrinologist so that i can get prescribed androgel or testosterone shots.

Just wondering, how likely is it that your family doctor will tell you to see a urologist/endrocrinologist if your regular and free testosterone levels are below 300ng/dl? I know for medical costs, doctor's won't refer most people to these types of specialists unless their situations are dire, so that they can keep health care costs down.

Sidenote: I personally believe that my regular and free testosterone levels are below 100ng/dl.

Any help or constructive advice would be really great, seriously. thanks

Additional Details

I don't know if I should say this or not, but in addition to feeling Extremely fatigued/lethargic, depressed, mood swings/irritable, anxiety and experiencing extremely dry skin, muscle loss, poor sleep, diminished hair growth, having trouble remembering and concentrating on anything (even the most basic of tasks), and frequent urination....my testicles have shrunken to the size of medium-seized grapes in a matter of months. So I'm positive that my testicular atrophy is being caused by primary hypogonadism.

5 months ago, in May, I was 5'8", 142 lbs, and a medium build. Now 4 months later (september), I'm 5'6", 126 lbs, and I'm very skinny now. I'm 18 years old, and I looked like I was 16 in May, but I now seriously look like a 12 year old.

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up ur iodine intake and it will help support the other functions of your body 50 mg at least a day higher side is the safer side