# Create a subtitle with titling for use with fancyhdr

I'm new to LaTeX and am trying to create a subtitle for a document. I'm using the titling package because it propagates values like the document title, author name, etc. even after maketitle is called. I want to use the subtitle as part of the header I've defined using the fancyhdr package. While I've been able to create and format the subtitle as I like I cannot figure out how to make its value available for use later in the document. Here is a minimal working example of what I have been able to build so far:

\documentclass{article}

\usepackage{titling}
\usepackage{fancyhdr}
\usepackage{lipsum}

%define subtitle command
\newcommand{\subtitle}[1]{%
\posttitle{%
\par\end{center}
\begin{center}\Large#1\end{center}
\vskip0.5em%
}
}

\title{Paper Title}
\subtitle{Paper Sub-title}
\author{Author Name}
\date{\today}

\pagestyle{fancy}

I've tried exporting the subtitle value by adding \def \thesubtitle#1% in the new subtitle command and then using\lhead{\thesubtitle} in the preamble to generate the header I want but I get no output from it. I'm sure I'm missing something simple and would appreciate any help.