How do PRP treatments keep hair on your head when the follicles that are missing are genetically predisposed to miniaturization?

Thank you for your question. You are asking how can PRP keep hair in areas where they are genetically predisposed to miniaturization. Through biopsy, you are confirmed to have androgenetic alopecia. You also indicate you have been on spironolactone.
I can certainly give you some guidance about this. I’m a Board Certified Cosmetic Surgeon and Fellowship-trained Oculoplastic Surgeon. I’ve been in practice in Manhattan and Long Island for over 20 years. I’ve been performing hair transplants since I started my practice. I’m also the founder of TrichoStem Hair Regeneration Centers, based on a system we developed that uses extracellular matrix and PRP for non-surgical treatment of pattern hair loss for men and women since 2011. We have patients from around the world who come to see us for this treatment.
You do seem well-versed in pattern loss, and approach it very logically. In my experience, PRP alone does not thicken thinning hair, but it is proven to stimulate short-term hair growth. You are correct in that PRP does need to be continually done. However, experience with patients who had PRP alone done elsewhere has shown that results of PRP are difficult to sustain, even with multiple and ongoing treatments. Patients also don’t have the patience, time, and pain threshold to regularly have scalp injections.
We do things differently in our practice using a PRP combination with extracellular matrix by ACell. Extracellular matrix is the main ingredient of our treatment, and PRP is the activator. Our treatment called Hair Regeneration has shown since 2011 as I was a pioneer of this injection treatment to thicken thinning hair, and stimulate growth from dormant hair follicles that are still viable, but not have been growing hair for a period of less than 5 years. While the cause of female pattern hair loss is not yet determined, and the mechanism of our treatment is not yet quite clear, it does appear to renew a healthy hair growth cycle using a wound healing mechanism. Both PRP and extracellular matrix are wound healing materials. The body naturally has a wound healing response, such as collagen production in healing cuts and burns. With a wound healing response, we have been able to achieve a renewed hair growth cycle, so thinning hair grows back in thicker, and stimulate growth from hair follicles that have not been growing. It sounds theoretical, but for going on 8 years, we have seen thicker scalp coverage and growth in over 99% of our pattern hair loss patients, both men and women. We have achieved this in one treatment session, with sometimes a booster in the second year, to sustain thicker hair growth for 3-5 years, sometimes even longer.
You are also correct that hair is genetically predisposed to thinning in people with pattern hair loss. The Hair Regeneration treatment is not a cure for hair loss, because there is no cure. Pattern hair loss is hardwired into the DNA, so it can’t be cured. However, we can manage hair loss so we can make hair as thick as possible, for as long as possible, so you can sustain thicker hair growth than you would without treatment. Our female Hair Regeneration do not need to use spironolactone or minoxidil, but you may need to repeat the treatment about every 5-6 years or so to keep thicker hair coverage for as long as possible.
You can meet with doctors who perform treatments beyond just PRP. It is important to note that not all PRP+ACell treatments are the same, even though they sound like the same treatment. We customize each treatment based on an algorithm I established that factors gender, current age, age of onset of hair loss, degree of hair loss, and other medical treatments used, like spironolactone in your case. I have found that most practices using PRP+ACell treatments are using the same formulation applied to all degrees of hair loss, in all ages, and perhaps with the same formulation for men and women. I hope you found this information helpful. Thank you for your question.

When prepared correctly, a high density PRP contains a concentration of growth factors and other beneficial factors such as cytokines that override most hair loss issues when hair loss is less than 2 years old. From 3 - 5 years, the abilities of PRP begins to drop off significantly. 
From a look at the photos and your explanation, I'm thinking you have more going on than androgenetic alopecia alone. 
I recommend locating an Integrative of Functional Medicine "MD" that also practices Bio-Identical Hormonal Replacement Therapy. Once they have treated you for a few months, then try the PRP hair regeneration.  I believe your results will be superior if you proceed in this manner.
Wishing you a great outcome.
Warmly,
Arbella Sarkis, MD