Ivar Asbjørn Følling

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Ivar Asbjørn Følling (23 August 1888 – 24 January 1973) was a Norwegian physician and biochemist who first described the disease named after him—Følling's disease[1]—which is better known outside of Norway as phenylketonuria or, for short, PKU.[2] He was born in Kvam, Steinkjer.


Følling studied chemistry at The Norwegian Institute of Technology in Trondheim and graduated in 1916. He then went to the Kristiania University in Oslo, graduating in medicine in 1922. He received his medical doctorate (somewhat like a PhD in Medicine) in 1929 after doing postgraduate work in Norway and abroad (in Denmark, England, Vienna and the U.S.). Starting in 1932 Følling occupied a series of medical posts in Oslo, culminating in his being Professor of Biochemistry and Physician-in-Chief at the central laboratory at the Rikshospitalet, which is the Norwegian national research hospital. He retired in 1958.


In 1934 at Rikshospitalet, Følling saw a young woman named Borgny Egeland. She had two children, Liv and Dag, who had been normal at birth but subsequently developed mental retardation. When Dag was about a year old, the mother noticed a strong smell to his urine. Følling obtained urine samples from the children and, after many tests, he found that the substance causing the odor in the urine was phenylpyruvic acid. The children, he concluded, had excess phenylpyruvic acid in the urine, the condition which came to be called phenylketonuria (PKU).

This abnormal condition reflects an inability to break down the amino acid phenylalanine due to an hereditary deficiency of the necessary enzyme which is called phenylalanine hydroxylase.

Today a screening blood test for PKU is done on newborns to detect the disease. With a special diet low in phenylalanine, PKU newborns can grow and develop into normal children and adults.


Følling's brilliant work was too late to save Liv and Dag from severe progressive mental retardation (and in Dag's case, death) but it has saved thousands of children since then.

It has been said that: "Følling is by many considered the most important medical scientist not to receive the Nobel Prize for Physiology or Medicine."[1]


  1. ^ Centerwall, S. A.; Centerwall, W. R. (2000). "The discovery of phenylketonuria: the story of a young couple, two affected children, and a scientist". Pediatrics. 105 (1 Pt 1): 89–103. PMID 10617710. doi:10.1542/peds.105.1.89. 
  2. ^ Fölling, Asbjörn. "Über Ausscheidung von Phenylbrenztraubensäure in den Harn als Stoffwechselanomalie in Verbindung mit Imbezillität.". Hoppe-Seyler´s Zeitschrift für physiologische Chemie. 227 (1-4): 169–181. doi:10.1515/bchm2.1934.227.1-4.169.