How to get from a Request type id an issue type id associated

Hi,
I have to get from a Request type id related to the issue type.
I have tried to see API about service desk but I can’t find a solution.
Right now I can retrieve the id of the request type from JIRA Service Desk REST API Reference (JIRA Service Desk 3.6.2) from this I can get a lot of information like project id, service desk id, request type id, request type name etcetera. But the information missing, It’s issue type id.
Is there any method to get the issue type id related to the request type?
Furthermore,
I can’t use a similar method (RequestTypeService (JIRA Service Desk API 3.9.0 API)) that concern a user action.
Because I have to implement it in a plugin and this method has to work without permission restriction.