Hi Aloha! I think there's quite a few of us around on MN with thyroid problems after pregnancy. I was diagnosed as hypothyroid 5 months after the birh of ds1. My TSH at the time was 14. I had been walking around like a zombie, brainfogged, exhausted, feeling ice-cold all the time, not losing any of my baby weight, and feeling down. Wouldn't say I was very depressed, but probably bordering it, as I hardly could get myself to leave the house. It was really my parents who diagnosed me, as they noticed the swelling at my throat. I have a brother who's hypothyroid and on thyroxin too, and my mum has just been diagnosed but her gp is refusing treatment, as he thinks she's only borderline hypothyroid (TSH5), although she has all the symptoms (weight, cold, fog, etc). Anyway, gp did bloodtest and diagnosed straight away, and put me on thyroxin. I was amazed at the difference: in a under a week i felt 1000x better! Also, it took until my thyroxin levels were sorted for my periods to come back.
Ds2 was born in December 2005 and my hypothyroidism was monitored very closely during the pregnancy. After the birth I had a very short period of being hyperthyroid, when i lost about 20kg in 2 weeks. I am sure those on a diet would be envious.... but i wasn't sure what had hit me at the time.. Now i am back to being hypothyroid, and my dose has only slightly gone up compared to what i started on. After having ds1 and first being diagnosed the gp told me that there was a chance that it would be a transient condition, but unfortunately for me this wasn't the case. I have since been diagnosed officially as suffering from Hashimoto's hypothyroidism (which is an autoimmune disorder), and this means i will need to be on thyroxin all my life. Considering this seems to run in my family, with both my mum and brother suffering from the same thing, you can only wonder if it really was the pregnancy that caused it... Probably not, but it just aggrevated it. Anyway, hypothyroidism is something that is quite easy to live with, as long as you are properly supplemented with thyroxin.
Great that you are going to take this one up and write about it. I think you are right in thinking there are loads of women misdiagnosed or undiagnosed. Am not just thinking about PND here, but also about those who try for number 2 and can't due to anovulation/drop in fertility (as Flip mentions).