Include subdomain when proxying in node

I've setup a simple HTTPS server to handle the following to situations:

1. Requests to https://localhost:5000/ that have a matching file in my directory are served via connect.static(__dirname). This works great for everything like my index.html and my CSS files and is working exactly as I need.

2. Requests to https://localhost:5000/api should redirect to https://subdomain.mydomain.com:443/api.

The proxy is properly transferring everything over HTTPS and the SSL handshake part seems to be working exactly as I would expect. The problem is that my API uses the subdomain to determine what database to connect to and what data to return. So, my API sees the request

https://localhost:5000/api/something

instead of

https://subdomain.mydomain.com/api/something

and is throwing an error telling me I have to supply the subdomain.

How can I tell the node proxy to forward (or use) the domain/subdomain when doing the proxy?

Here is my code:

var fs = require('fs');
var connect = require('connect'),
    https = require('https'),
    httpProxy = require('http-proxy'),
    options = {
      key: fs.readFileSync('key.pem'),
      cert: fs.readFileSync('cert.pem')
    },
    endpoint = {
        host: 'subdomain.mydomain.com',
        port: 443,
        prefix: '/api',
        target: { https: true }
    };

var proxy = new httpProxy.RoutingProxy();
var app = connect()
    .use(connect.logger('dev'))
    .use(function(req, res, next) {
        if (req.url.indexOf(endpoint.prefix) === 0) {
            proxy.proxyRequest(req, res, endpoint); 
        } else {
            next();
        }   
    })  
    .use(connect.static(__dirname));

https.createServer(options, app).listen(5000);
console.log('Listening on port 5000');