Male hormone axis
Testosterone
The main androgen circulating in your blood, most of it carried bound to proteins. It peaks in the early morning and falls through the day.
Free testosterone (calculated)
The fraction of your testosterone that is not bound to carrier proteins, calculated from your total testosterone, SHBG and albumin.
SHBG
The protein that binds testosterone and oestrogen in the blood and decides how much is left free. It moves with thyroid hormone, insulin and the contraceptive pill.
LH
A pituitary hormone that triggers ovulation in women and signals the testes to make testosterone in men.
FSH
A pituitary hormone that tells the ovaries or testes to do their work. In women it moves through the menstrual cycle.
Prolactin
A pituitary hormone best known for milk production, which also rises with sleep, exercise, a stressful blood draw and several common medicines.
DHEA-S
An adrenal hormone the body uses as raw material for other sex hormones. It peaks in your twenties and falls steadily with age.
Free androgen index (calculated)
The ratio of your total testosterone to SHBG, used as a rough read of how much androgen is left unbound.
Albumin
The main protein your liver makes to hold fluid inside blood vessels and carry hormones and minerals around.


