drupal 7 user registration custom url returning a blank page
You can't call a hook in hook_menu(). You can either create an alias for the user registration page or replace your menu item with:

function medical_reg_user_register_menu() {
  $items['page/medical'] = array(
    'page callback' =&gt; 'drupal_get_form',
    'page arguments' =&gt; array('user_register_form'),
    'access arguments' =&gt; array('access content'),
    'type' =&gt; MENU_CALLBACK
    );
  return $items;
}