This test measures the amount of dihydrotestosterone (DHT) in the blood.  Low DHT has been associated with low libido and high DHT has been linked to acne, hair loss and benign prostatic inflammation in a minority of men.

To find out if sperm count is normalized in men using hCG plus TRT, several studies have found that 17OH-P blood level is correlated to intratesticular testosterone (ITT) required for the testicles to make sperm, so testing for this hormone could not only save time while optimizing HCG dose/frequency but also eliminate the need to perform testicular aspirations, a very difficult procedure to do. Sperm count does not stabilize until 6-8 weeks after starting hCG plus TRT, so knowing your 17OH-progesterone blood level can give you a quick way to determine if your hCG dose and frequency is adequate before your first follow-up semen analysis after 8 weeks.

Insulin-like Growth Factor 1, also known as IGF-1, is used as a biomarker for blood levels of human growth hormone. It is a hormone produced by the liver and other tissues which affects growth-promoting activities and glucose metabolism. The blood level of IGF-1 appears to fluctuate over 24 hours and is found to be related to growth hormone secretion.