Hi, this is Tom from zero to finals.com. In this video, I'm going to be going through testosterone,

and you can find written notes on this topic at zero to finals.com slash testosterone or in the zero to finals

endocrine system book. And you can find flashcards and questions to train your knowledge on this content

and help you remember the information for longer at members.0.0.com.

So let's jump straight in.

Testosterone is the primary male sex hormone.

Testosterone is an androgen, meaning a male sex hormone, that acts on the androgen receptors.

It's a steroid hormone, and it's anabolic hormone, meaning a building hormone.

Testosterone can be converted to dihydrotestosterone or dhattie in the tissues by an enzyme

called 5 alpha reductase, particularly in the liver, prostate and skin.

Dihydro testosterone is a particularly potent androgen hormone with stronger effects than

testosterone. Let's talk about the production of testosterone. The lay dig cells in the testes

produce more than 95% of the testosterone in males. Testosterone is also produced in smaller quantities

by the adrenal cortex or the outer part of the adrenal glands and the ovaries in females.

Cholesterol is the starting point for most steroid hormones. Cholesterol is the starting point for most steroid hormones.

Cholesterol is converted through various different precursor molecules with the help of specific enzymes

to become a variety of steroid hormones, including testosterone, progesterone, estrogen, cortisol, and aldosterone.

Some clinical relevance for you. Congenital adrenal hyperplasia is a genetic condition caused by a

congenital deficiency of the 21 hydroxylase enzyme.

21 hydroxylase is the enzyme responsible for an essential step in the creation of aldosterone and

cortisol.

Deficiency in the 21 hydroxylase enzyme means that precursor molecules, specifically 17 hydroxyprogesterone and

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