could anyone advise me as to whether the below diseases are at large and a problem in leonbergers:

Addison's Disease
Hypothyroidism
Laryngeal Paralysis/Polyneuropathy
Panosteitis

Thanks

Can find that the first two and the last have been recorded in the Leonberger but not as far as I have found, Laryngeal Paralysis/Polyneuropathy, but records are being updated all the time.

Unfortunately, LP/NP has been found in leonbergers, and there is research going on at the moment so we can understand more about this disease. Many people assume it is 'natural' for an older dog to have breathing problems and rear weakness simply because they are old. Not many old dogs have biopsies and because of this it is difficult to know how many cases are missed.
The club is now doing a survey to see how many dogs could be affected.  Very sad.