There is no possibility to re-name the IoT Hub hostname URL. However, you can migrate/clone an Azure IoT hub to another region by exporting/using existing template. Using this template, you can create a new IoT Hub with the required name. Please see How to clone an Azure IoT hub to another region for more details and things to consider before cloning.
Please note that, IoT Hub doesn’t support dots in the hostname. As per the Naming rules and restrictions it should contain only alphanumeric and hyphens and can't end with hyphen.
Also, currently custom domain name support is not available. If you are looking for this feature, kindly provide your feedback on the UserVoice and upvote for this feature.
Do let us know if you have further queries.
Source: MSDN