My husband knows about my diagnosis. So does my sister.
I have not told about it to any of my friends. My mother does not know. Sometimes I feel that I should tell about it, as it could explain some of my behaviour or make an excuse when I'm too tired or agitated to meet them. As for friends I'm afraid they would not like to see me much if they knew. For mom - we are not very close, we meet only several times a year. She has her own health issues and extra stress would do no good to her. Probably the relieving on my illness would be more like insult to her, for how little she knows me, how little she has been there for me in hard times etc.
Hard to keep silent and hard not to. Also I fear that they may notice my pills or prescriptions or whatever, which I usually put out of reach and out of sight, but you never know.