function give_profile_name($atts){
$user=wp_get_current_user();
$name=$user->user_firstname .' '. $user->user_lastname ;
return $name;
}

add_shortcode('profile_name', 'give_profile_name');

add_filter( 'wp_nav_menu_objects', 'my_dynamic_menu_items' );
function my_dynamic_menu_items( $menu_items ) {
foreach ( $menu_items as $menu_item ) {
    if ( '#profile_name#' == $menu_item->title ) {
        global $shortcode_tags;
        if ( isset( $shortcode_tags['profile_name'] ) ) {
            // Or do_shortcode(), if you must.
            $menu_item->title = call_user_func( $shortcode_tags['profile_name'] );
        }
    }
}

return $menu_items;
}