Are there organisations in Switzerland who provide private blood tests, eg vitamins, endocrine results etc?

They're popping up a lot in the UK and I wondered if they operated here too.

Do you mean a somewhere other than a doctor’s practice / endocrinologist?

Most doctors do basic blood analysis in-house but for extensive testing they send it on to the lab.

There is one Zürich walk-in lab

https://www.walkin-labor.ch/laboranalysen/index.php

https://unilabs.ch/fr/patients

They do the testing for the doctors .. But you can just go direct i think.

Yes, you can attend labs for private blood tests. Its often good to visit a Dr first thought in order to prescribe the required test.

I had several private tests done at Unilabs while travelling in Switzerland, which I simply paid for directly. The price of the tests was indicated prior to the sample being taken for approval.
https://unilabs.ch/fr?lng=fr