Problem displaying a custom uitableviewcell content

I've a custom UITableViewCell with a UITextView in it. The cell grows dinamically with the uitableview as user enters text.When I display the table, I have to calculate the height of the custom cell depending on the content text entered by the user, so in the

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath[/CODE]

I use:

CGSize textSize = [myString sizeWithFont:[UIFont systemFontOfSize:17.0f]  constrainedToSize:CGSizeMake(320, CGFLOAT_MAX) lineBreakMode:UILineBreakModeWordWrap];return textSize.height;

The returned height seems correct, but the not visible text is truncated.