Steroid hormones like testosterone and estrogen can alter gene expression and influence traits such as muscle growth.

“in fact the steroid hormones refers to estrogen testosterone of the sort that we all make that men and women make naturally and those steroid hormones can impact gene expression they can are of course what turns on the growth of the of the breast tissue of the testicular tissue of the hair growth and on and on and that's all because of gene expression if you're really going to change the identity and function of a cell long term right you're going to literally change the breast tissue or change the penile tissue or change the ovarian tissue in some sort of consistent way across the lifespan you can bet that there are changes in gene expression”

“the steroid hormones like testosterone estrogen and others they combine to cell surface receptors but they can also go into the nucleus of a cell itself and cause changes in expression which is sort of if you just think about puberty is the most Salient example right there's all these latent potential in the cells of the body but then once the testosterone and dihydro testosterone and estrogen arrives in the body depending on the on the the sex of the individual then you activate hair growth you activate breast growth you activate muscle growth thickening of the vocal anyway that's through Gene uh changes and gene expression”

“so they can change the sorts of things that cells will become and they can change the way that cells function in a long-term way and that's actually how the presence of these genes like Sr and mulian inhibiting hormone lead to reductions or elimination I should say of things like the mulian ducts and promote instead what's called in males the wolfian ducks or promote the uh the development of testes rather than ovaries”