The Great Depression of 1929 made it hard for his family to support his education, but his sisters managed to pay for it with their salaries.
From 1943 Conn took on the Division of Endocrinology and started an investigation concerning acclimatization of military personnel to warm climates like in the South Pacific.
At the Presidential address to the Society of Clinical Research Conn presented a thirty-four-year-old patient complaining of episodic weakness of the lower legs, almost to paralysis, with periodic muscle spasms and cramps in her hands for a total period of seven years.
There were elevated levels of aldosterone in her circulation, coming from a hormone producing adrenal adenoma.
Conn wrote a total of 284 articles and book chapters and was recognized as a tutor stimulating others in research.