Kallmann's syndrome has one key symptom that sets it apart from other forms of hypogonadotrophic hypogonadism; the lack of sense of smell.

The absence of the sense of smell (anosmia), or a vastly reduced sense of smell (hyposmia) could act as marker that can lead to a diagnosis of Kallmann’s syndrome. Reduced sense of smell can happen on its own for a number of other reasons but in conjunction with delayed puberty might lead a doctor to suspect a case of Kallmann’s syndrome.

The sense of smell can easily be tested for by a combination of two simple tests.

One is a basic alcohol smell taste which uses different concentrations of the same smell, normally alcohol, to detect the threshold at which the smell is detected.

The other test is a more involved test involving a range of different smells to see which can be identified correctly.
A commonly used test is the University of Pennsylvania Smell Identification Test (UPSIT).

This involves a scoring method on the above tests and gives a score of between 0 and 100.

A perfect score would be 100.
0–10 is considered anosmia.
10–40 severely hyposmic.
40–60 moderately hyposmic.
60–90 mildly hyposmic.
90–100 is considered normal.