By default, WordPress do not allows shortcodes to be executed inside custom fields. If for some reason you need to be able to execute a shortcode inside a specific custom field, here is an easy way to do it.

Just put this code into whatever page you are displaying the results of the shortcode, and change the your_custom_field_here to the name of your custom field.

 <?php echo apply_filters('the_content', get_post_meta($post->ID, 'your_custom_field_here', true)); ?> 

Credit: Snipplr.