Perimenopausal hair thinning

I'm in the same boat and I've been doing two things recently that have made a huge difference! I use a serum from Young Living called Progessence Plus which has made a difference to various symptoms, and for the hair loss, I have been drinking something that a doctor whose name I forget, called "the red drink". It is a combination of a supplement called Sulfurzyme, Ningxia Red and water. The supplement contains MSM, which our body begins to lose, and therefore, the taking of it helps reduce and in fact reverses hair loss to a degree. The Ningxia Red is an antioxidant-rich, nutrient dense drink supplement that helps the body restore glutathione, and makes the supplement more bioavailable on account of it's unique ingredient combination. Happy to chat more about the science of the supplements if you have questions!

Sorry about your hair experience, I had the same awfulness, even my eyelashes were dropping.   Biotin really helped/helps--and it's simply a good supplement to take no matter. (Google to find out.)  Also, I became more consistent in my daily meditation & general health habits (water drinking, walking or other gentle exercise, sleep, food choices etc)  Ever consider finding a different doctor ??-- I like Dr. Goo at Berkeley Family Practice, while not perfect (wish she were a "functional" doc; mine/Dr. Sarah Ferguson, moved to Washington & since then I've sorta been my own doc (that's a long story) Anyway, it is 'okay' to let a doc 'go'.  Once  I realized that I'm the captain of my health team, then I let go players who didn't support (or mostly support) my vision of a team's unity, it's vision and philosophy of life. Of course, there will be times one needs a conventional doc, but I don't feel that doing menopause with a straight & narrow doc is a period for feeling pressured by him/her.  What about googling "functional physician" "Integrative health" per your insurance company, there are some great ones in San Francisco.  --- All the best.

Two things to look at:

First, thyroid function. Something like 10% of women develop autoimmune thyroid disease, with diagnosis typically in middle age. One of the symptoms is hair loss.  It can be a bit tricky to diagnose, because like other autoimmune conditions it can wax and wane.  When I was diagnosed, the obvious symptom was rough-textured hair that was coming out.  The initial test (for thyroid hormone levels) was negative -- but the test for autoimmune antibodies was positive.  Treatment is thyroid-hormone pills.  There may be other hormonal conditions (other than perimenopause) that can cause hair loss, as well as other medical conditions.

Second: Rogaine (aka minoxidil), the stuff balding guys sometimes use. There is also Rogaine for women.  It works for some types of hair loss, I don't know how well, the main drawback being the cost as the hair loss returns if the Rogaine is stopped.

Rogaine!  You can get it at Target (though sometimes out of stock).  My doctor told me it doesn't always work, but it is working well for me, after 3 months.

I was having this problem and thought it was due to aging/perimenopause. Then I realized that it had begun shortly after I began to use a strong over the counter retinol product on my skin. I read that too much vitamin A can cause hair loss and I found anecdotal reports that retinol seems to cause hair loss in some people. I quit using the skin product and my hair went completely back to normal. 

Hair loss can be a symptom of iron deficiency.  I'd have your PCP check your iron level.