What's wrong with me?

Short story: I have to fill in an insurance claim form (UK), and want to add information about my tg side. Gender Identity Disorder? No. I'm quite sure what my gender identity is, thank you. So what can I call it so an insurance suit understands?

Long story: I have Fibromyalgia, and discovered by accident shortly after diagnosis that there's a waiver of premium clause in some of my insurance policies. This means I haven't been sending them money since this started four years ago, but they need a declaration every year to enable the waiver to continue.

There's all kinds of legal guff about making sure I fill out the form completely and honestly - which I do. I haven't mentioned my tg side at all so far, as I hadn't thought about emerging from the chrysalis until some time after my enforced idleness started, and it didn't seem relevant, but it occurred to me that mentioning it now (as a sort of side note) might not be a bad idea.

Problem is, what do I say? As I mentioned above, I don't think GID covers it properly. I'm not in the US, so I don't think anything on the Prescribed List of Actual Diseases or whatever it's called over there will be appropriate. The word 'Transgender' is a bit vague and probably doesn't convey what I want to say.

Do others here have any more experience of this kind of detail? When you write to officialdom, what do you say? I'm not currently undergoing or planning transition, even though that's a medium to long-term goal. I'm not entirely in the closet, and frankly I'm getting to the point where I don't care either way.

Thank you in advance for your thoughts.

Penny