(covers information from several alternate timelines)
A hypothalamic series was a medical test involving the hypothalamus.
In 2370, Dr. Beverly Crusher ordered a hypothalamic series to be run on Deanna Troi, whose body temperature had dropped several degress below normal. Unbeknownst to Troi and Crusher at the time, Deanna was suffering from the initial stages of Barclay's Protomorphosis Syndrome. (TNG: "Genesis")