Common wisdom would advise that right now is not a good time for you to do far-reaching important decisions, and I'd extrapolate this to mean also that it is not a good time for exams.

If you think this is better for you, i.e., your recovery*, you can of course try to negotiate/decide together with the head of the committee to give it a try and see and either do the viva as planned if you are lucky and recover faster than it looks now or postpone it last minute. This option is fine if everyone is fine with it - it is unlikely to work if you have an external examiner coming from far away.
Openly and transparently deciding to give it a try will automatically also make them aware that you have health issues that may affect your performance.

Someone else being uncomfortable with details they may hear from you is an additional protection for you. I'd say it is a 2nd line of defense that we have built-in (biologically or culturally?), in case your own do-not-share protection isn't working well, e.g. due to sickness or in case you cannot not share because illness or disability is obvious*.
Thus, you don't need to worry about their comfort - and anyways, I expect your comfort with sharing should stop you earlier.

They are all professionals and have been examiners many times (even should that be their first time examining at a viva) and thus have experience dealing professionally with life (and death :-( ) as it happens to affect exams and other aspects of professional life. Note: if all works as professionally as expected and noiselessly, you rarely hear about this unless you are affected.

Common wisdom would advise that right now is not a good time for you to do far-reaching important decisions, and I'd extrapolate this to mean also that it is not a good time for exams that you take very seriously.

If you think this is better for you*, you can of course try to negotiate/decide together with the head of the committee to give it a try and see and either do the viva as planned if you are lucky and recover faster than it looks now or postpone it last minute. This option is fine if everyone is fine with it - it is unlikely to work if you have an external examiner coming from far away.
Openly and transparently deciding to give it a try will automatically also make them aware that you have health issues that may affect your performance.

Someone else being uncomfortable with details they may hear from you is an additional protection for you. I'd say it is a 2nd line of defense that we have built-in (biologically or culturally?), in case your own do-not-share protection isn't working well, e.g. due to sickness or in case you cannot not share because illness or disability is obvious*.
Thus, their comfort is not yours to need and worry about. (And anyways, I expect your comfort with sharing should stop you earlier.)

They are professionals and have been in exams many times and thus have experience dealing professionally with life (and death :-( ) as it happens to affect exams and other aspects of professional life. 

Note: if all works as professionally as expected and noiselessly, you rarely hear about this unless you are affected.

Since you write that your issues are caused by the abrupt hormonal changes, what does your MD say about the expected time frame? They may tell you a time frame that means you should reschedule your viva without any further thought and they should then also give you an attestation saying that.
(Remember that there are medical conditions where one oneself doesn't properly sense/realize that one shouldn't e.g. do exams)

Common wisdom would advise that right now is not a good time for you to do far-reaching important decisions, and I'd extrapolate this to mean also that it is not a good time for exams.

Time frame

Otherwise, if you think you may be sufficiently recovered, I'd recommend to notify your advisor and/or the head of your exam committee that health-wise, you'd not be able to do the viva now, and that you cannot predict whether you'll be sufficiently recovered by then.
It would be good to do this ASAP since for the examiners it is much better to know 2 weeks earlier that the exam needs to be rescheduled. Particularly if the committee has external members that need to travel.

If your committee is entirely local, and you think this is better for you, you may negotiate/decide together with the head of the committee to try and see and either do the viva as planned if you are lucky and recover faster than it looks now or postpone it last minute. This option is fine if everyone is fine with it. Most importantly, this everyone includes you: if the approaching exam puts you under pressure, that will likely not help your recovery. Openly and transparently deciding this will automatically also make them aware that you have health issues that may affect your performance.

Common wisdom would advise that right now is not a good time for you to do far-reaching important decisions, and I'd extrapolate this to mean also that it is not a good time for exams.

Time frame

Since you write that your issues are caused by the abrupt hormonal changes, what does your MD say about the expected time frame? They may tell you should reschedule your viva and they should then also give you an attestation saying that.
(Remember that there are medical conditions where one oneself doesn't properly sense/realize that one shouldn't e.g. do exams)

I'd recommend to notify your advisor and/or the head of your exam committee and/or the exam office ASAP since for the examiners it is much better to know 2 weeks earlier that the exam needs to be rescheduled. Particularly if the committee has external members that need to travel.

So, tell them that health-wise, you'd not be able to do the viva now, and that you cannot expect to/predict whether you'll be sufficiently recovered by then.

If you think this is better for you, i.e., your recovery*, you can of course try to negotiate/decide together with the head of the committee to give it a try and see and either do the viva as planned if you are lucky and recover faster than it looks now or postpone it last minute. This option is fine if everyone is fine with it - it is unlikely to work if you have an external examiner coming from far away.
Openly and transparently deciding to give it a try will automatically also make them aware that you have health issues that may affect your performance.

* Maybe your recovery will be faster if the pressure of the viva is not lurking in the future - regardless of whether you reach your full (when healthy) potential (=> grit teeth and over with it in order to put that additional obstacle out of the way of your recovery). Or maybe your recovery is hindered by the pressure of the closely approaching viva or potentially later by a hindsight regret that you may have done better in the viva had it been postponed (=> get this obstacle out of the way of your recovery by canceling it for now, and reschedule when you are sufficiently recovered). Or ...
Only you can judge for yourself which way to go. But both options are fine in general.