Linds, the hair on the head is affected by either hormones or our general well being, while our leg and underarm and pubic area hair is simply there for a reason (likely to protect us way back in the caveman era when we didnt wear clothes/underwear!!). That's why if you ever get electrolysis on your underarms, legs, bikini area it is so easy to get rid of as it is not hair which is affected by our hormones.
As for when do you see regrowth.......my ferretin dropped as far as 8 and my hair was still struggling to regrow. There were baby hairs growing out, but they wouldn't last the distance. I noticed my hair which had normally grown close to waist length was only making it to my bra strap or just below bra strap, but was beginning to look straggly at the ends. On my scalp i had about a million varying hair lengths and they would stick out, most would end up falling out.
For me personally, i noticed this weird hair loss phenomenon start occuring when my ferretin was 35. That was the very first time a doctor decided to do a blood test regarding my hair loss. The doctor was happy with 35 and even though it kept dropping, he never questioned why it was dropping or the fact that it could be affecting my hair loss and my increasing depressed state plus my general tiredness and lack of motivation and that was when my monthly cycles began getting screwed up too. I have since learnt that iron deficiency can affect some womens cycles.
In april 2006 my ferretin was 8 and in about august of 2007 it did get to 35 at one stage and i did notice in mid december of last year that it suddenly wasnt falling out as much as it normally did around that time of year (it being summer here) It's still shedding, but it's closer to a normal amount of shedding than what it has been like in previous years. Previously i could have collected the hair and made toupes for bald men!! Could have made one per week at the rate i was losing it
So now i believe my ferretin must be 40 or could be little higher and i'm using my hair shedding as a sort of guage considering i have often heard that it stops shedding unrealistically at around 40, but you dont see proper cycles of hair growth until you get to 70 or higher and stay there. Hair has 3 basic stages, the growing stage, resting stage and i think the fall out stage and all of this is supposed to happen in a proper cycle, but when ferretin gets low it disrupts this cycle and you find you have difficulty growing your hair or its dry and brittle, it thins, falls out more than before, falls out before it's scheduled time etc etc.
Best you can do is keep at the iron supplements, verify with your doctor that you dont have any other medical conditions, watch what you eat/drink as certain foods/beverages can interfere with iron absorbtion. It all takes time and patience so dont give up