I've recently been diagnosed with postpartum thyroiditis and hope this may be helpful to others.
I gave birth to my DS at the beginning of the year. I had a difficult pregnancy. 10 weeks in my appendix ruptured and I had to have an operation to remove it, I had nausea every day for nine months and suffered from very painful SPD. To top it off I went through a full labour only to end up having an emergency c-section due to complications. Everything worked out okay, baby and I were fine.
After all I'd been through, I fully expected to feel like rubbish after the birth! In the first few months I felt continuously exhausted and anxious and I kept getting an arthritis type pain in my hands. Knowing how much strain pregnancy puts on your body, I thought this was probably normal for a new mum. But things didn't improve, I still felt weak and exhausted and the doctor suggested a blood test for anemia, which came back as normal. So I thought I'd better just get on with things, perhaps having a baby was going to be tougher than I'd imagined?!
A few more weeks ticked by and by now I was struggling to carry DS up the stairs, my thighs felt completely empty. I often woke up and felt like I had a "brain fog", the simplest of tasks seemed challenging. Then, when DS was around 5 months, I thought I was coming down with flu, it was like flu and a hangover all rolled into one. At worst I couldn?t get out of bed, I was even too weak to lift my knife and fork to eat, it was horrible and frightening. After a few days when I wasn?t getting any better the doctor sent me for blood tests which showed up that I have postpartum thyroiditis. Hurrah! I wasn't going mad after all, there was something wrong with me. After battling on for months it was such a relief they'd found something. My thyroxine levels had dipped to 3 (should be around 15-20), the doctor confirmed I hold the record for the lowest ever reading at the surgery, great!
It seems thyroid problems during or after pregnancy are fairly common. A few (B list 
) celebs Kate Garraway (GMTV) and Kirsty Gallacher have had similar problems. The exact cause is unknown, but its thought to be because the immune system changes during pregnancy. I have an autoimmune condition which means that my own antibodies have attacked my thyroid and stopped it functioning. Sometimes the condition is temporary and resolves itself after a few months, but the endocrinologist has told me I'll need to take the tablets for life.
I'm now taking 125 micrograms of thyroxine each day and am starting to feel a bit more human. I have to go back for regular blood tests to see if they've got the medication right as it takes a bit of fine tuning. I think the most difficult thing is getting diagnosed. So many of the symptoms are exactly what you'd expect after having a baby, hair loss, feeling like you always need more sleep, lack of energy etc.
Mentally its been tough. Before pregnancy I was a very fit and active person, so I've found it really difficult not not being able to do the most basic things, like not having the energy to walk round the block with the buggy. DH and my parents have been fantastic. I'm really lucky, without their help, I don't think I could have coped looking after DS whilst feeling so dreadful. It's a slow road to recovery, probably another 6 months before I'm fully recovered. But the condition is very manageable and I'm confident that at some point in the near future I may even feel well enough to go back to work.
Thankfully DS is a very happy and healthy little boy and hasn't been affected by my thyroid problems. We are enjoying every moment with him, he's absolutely the light of our lives. :)
Further info can be found at: www.btf-thyroid.org/