An investigation in http://www.patentbuddy.com/Inventor/Dittgen-Michael/6439758 shows 18 US Patents Issued, 25 US Applications Filed, 298 Total Citation Count, Jul 29, 2015 Most Recent Filing, Aug 31, 1994 Earliest Filing.
The assignees are Entec Gesellschaft für Endokrinologie Technologie m.b.H. (1994) 1 patent; Jenapharm GmbH & Co. KG (1995-2002); 10 patents; Schering AG (1999) 2 patents; LTS Lohmann Therapie-Systeme AG (1999-2006) 3 patents; Otto Bock Kunststoff Holding GmbH (2009) 2 patents; Bayer Pharma AG (2013), 1 patent; Bayer Intellectual Property GmbH (1996-2015) 12 patents.
I was working in „the Dittgen group“ creating a „Combination Compound for Contraception Based on Natural Estrogen“ http://www.ded.uscourts.gov/sites/default/files/opinions/lps/2016/july/12-1726.pdf
Approximately 60 results were found in the worldwide patent database for “michael dittgen” as the inventor in https://worldwide.espacenet.com/advancedSearch (Search performed at April, 2017).