Getting the permalink from a variable.

Hi,

I want to get the permalink from a given variable.

I have an option using the settings api in which users can input the slug of a page.

What i wanted is to output the permalink of the slug inputted by users.

I have this,

function mytheme_option( $option ) {
	$options = get_option( 'mytheme_options' );
	if ( isset( $options[$option] ) )
		return $options[$option];
	else
		return false;
}
$termspage = mytheme_option('terms_slug');
echo get_permalink($termspage);

However, it doesn’t output the permalink even the page of the inputted slug exists.

Please help