\documentclass{beamer}

\usepackage[nomain,acronym]{glossaries}

\newacronym{TEST}{TEST}{Test}

\makeglossaries

\newcounter{acronum}
\makeatletter
  \newglossarystyle{countentries}{%
    \setcounter{acronum}{0}
    \renewenvironment{theglossary}{}{}%
    \let\glossaryheader\@empty
    \let\glsgroupheading\@gobble
    \let\glsgrouptitle\@gobble
    \let\glsnavhypertarget\@gobbletwo
    \let\glsnavigation\@empty
    \let\glsgroupskip\@empty
    \let\glsentryitem\@gobble
    \let\glsentrycounterlabel\@empty
    \let\glstarget\@gobbletwo
    \let\glossaryentrynumbers\@gobble
    \let\subglossentry\@gobblethree
    \let\glssubentryitem\@gobble
    \let\glssubentrycounterlabel\@empty
    \let\currentglossary\@empty
    \renewcommand\glossarysection[2][]{}%
    \let\glossarypreamble\@empty
    \let\glossarypostamble\@empty
    \let\glsresetentrylist\@empty
    \renewcommand\glossentry[2]{\stepcounter{acronum}}%
  }
  \AtBeginDocument{\printacronyms[style=countentries]}
\makeatother

\begin{document}

\begin{frame}{1. slide}
\end{frame}

\end{document}
