It was on the initiative of Katsch that in 1930 a residential facility providing clinical and socio-medical care for Diabetic patients was established at Garz on the Island of Rügen.

Gerhardt Katsch is widely regarded –⁠ alongside Oskar Minkowski and Karl Stolte –⁠ as one of the three principal pioneers of modern diabetes management in Germany.

[3][4][5][6] As head of the Greifswald University Hospital (as the University Clinic has subsequently been renamed) and the longest serving medical officer at Greifswald, at the end of April 1945 Katsch was involved, together with Rudolf Petershagen, the local military commander, in a speculative visit to what remained of Anklam, where the rapidly advancing Red army was encamped.

[12] Notwithstanding speculation that emerged during and after the Hitler years in respect of his reportedly Jewish ancestry, sources citing contemporary information indicate that Gerhardt Katsch was born into a Protestant family.

[13] Through his paternal grandmother, born Caroline Helene Antoinette Auguste Andrée (1832-1916), Katsch had a family connection with Nîmes: he attended the francophone "French school" in Berlin.

His father had lost most of his wealth in 1906 after providing a three million mark financial guarantee for a friend who had been murdered, on account of which the whole amount had fallen due for payment.

[17] They married on 3 September 1917 close to the bride's home at Ottensen (which had still not, at that time, been subsumed into Altona and the Hamburg conurbation).

But this time Katsch stayed behind, taking on the role of Chief physician at the Clinic for Internal Medicine at the venerable Holy Ghost Hospital.

Katsch, having just entered his sixth decade, thereby became an SA member, appointed to the rank of "Oberscharführer" (loosely, "senior squadron leader") in the "SA-Reserve" during 1934.

[6] Called upon to explain this record after the political wind had again changed, Katsch did so: one "had to look for ways to protect oneself from multiple attacks, resulting most particularly from the fact that I had not - as I had been asked - found a pretext to dismiss a Jewish assistant".

[25] As the antisemitic "Law for the Restoration of the Professional Civil Service" was applied with increasing enthusiasm by the authorities, notwithstanding his SA involvement, Katsch lost a number of senior physicians at his clinic during the middle 1930s.

Katsch's own attestation, with appropriate genealogical back-up, that he descended from four "Aryan" grandparents went unchallenged by the authorities, which saved him from being branded as a "jüdischer Mischling zweiten Grades" ("semi-Jew") under the infamous antisemitic Nuremberg Laws.

[17] Nevertheless, finding himself under pressure from persisting rumours of his own Jewish ancestry, and no doubt fearing for the safety of his family,[17] in August 1934 Katsch also joined the SS as a "supporting member".

They may have been written with half an eye on future publication or at least on the possibility that they might fall into the hands of the German authorities, since they scrupulously avoid personal judgements.

This makes the coldly factual assessment that he recorded - for instance in his diary entry for 9 July 1943 - the catastrophic "nutritional status" of German war prisoners all the more chilling.

[2][17] At the instigation of Rudolf Petershagen, the local military commander, during the night of 29/30 April 1945 Gerhardt Katsch, as head of the University Clinic and senior medical officer at Greifswald, together with the University Rector Carl Engel and Colonel Max Otto Wurmbach (1885-1946), the deputy military commander responsible for Greifswald, were part of a small group of city representatives mandated to deliver a surrender offer to leaders of the advancing Soviet army.

Had Germany not formally capitulated a few days later, involvement in this breach of Adolf Hitler's instruction that Germans should “fight to the death” would have had seriously personal consequences for Katsch, one of the least of which would be the conclusion that he had, by his actions, voluntarily resigned his party membership.

[25] During October 1946 Gerhardt Katsch received the offer of a planned professorial teaching chair for Internal Medicine at the University of Mainz.

There was also a plan by the University of Berlin medical department to appoint Katsch as successor to his old teacher, Gustav von Bergmann, at the Charité.

Other family members fled towards the western part of Germany ahead of the advancing Red army and the rumours of atrocities against civilians accompanying its progress.

Schloss Karlsburg was used as a general purpose hospital and resettlement camp during 1945 and 1946, but in 1947 it was repurposed as a second residential treatment facility for diabetes patients, to be operated under Katsch's responsibility.

[31] At Sellin on shoreline beyond Garz on the Island of Rügen the first special school in the world designed for and dedicated to diabetic children was opened in 1955.

In 1950, in recognition of his reputation and contributions, he was granted, through a resolution of the ministerial council dated 12 October 1950, what was termed an "Einzelvertrag" (loosely, "unique deal") which gave him far reaching competences and privileges, including a teaching salary which he would continue to receive after reaching the state retirement age, and the opportunity to continue serving as director of the Institute at Karlsburg for life.

[4][34] His term of office coincided with the university's 500th anniversary celebrations, in which he participated some effect, notably in using the event as an opportunity to submit two letters to President Pieck (who at the time, despite his advancing years, was still formally head of state in the German Democratic Republic).

[10] Early in 1961, while on a winter break at his holiday home in the Allgäu, Gerhardt Katsch suffered what turned out to be a fatal heart attack.

[37] The "Garzer Thesen", which Katsch published less than twenty years after the discovery of insulin, was hugely influential and quickly came to define mainstream orthodoxy in respect of diabetes treatment in Germany (and beyond) for a generation.

[41] In terms of subsequent developments it nevertheless begged some important questions: one which stirred significant controversy through the 1940s, 50s and 60s, concerned the need to find an optimal balance between insulin dosages and nutrition.

The pediatrician Karl Stolte (1881-1951), who had been director of the children's clinic at the University of Breslau before 1945, found it necessary to add a refinement to Katsch's theses.

Based on his own experience of treating adults, Katsch had assumed that dietary choices should be significantly restricted in order to align with fixed insulin dosages.

By the time the controversy became heated, Germany was at war, and there were no opportunities available to develop and undertake appropriate experimentation, which under other circumstances might have resolved the issues arising.