'hypo' means below or under (as in hypodermic – below the skin). 'gonadal' means relating to the sex organs, i.e. the ovaries or testes. In this context the term implies that the sex organs have not developed into their normal state they would have achieved if puberty had occurred and are not responding in the usual post-pubertal manner in producing the normal sex hormones – oestrogen and testosterone.

The term hypogonadism covers a wide range of conditions and is not unique to Kallmann’s syndrome. There are more common genetic disorders that can result in hypogonadism such as Kleinfelter's syndrome and Turner’s syndrome. Hypogonadal conditions can be classed as either primary or secondary.

Primary hypogonadism is due to the sex organs themselves not functionally correctly or being unable to respond to the correct hormone signals. Kleinfelter's and Turner's are primary hypogonadism conditions.

There are other primary hypogonadal conditions that can occur during life where previously normally functional gonads stop producing their specific hormones. Certain types of drugs, mumps and physical injury can all cause primary hypogonadism during life.

Secondary hypogonadism is due a failure in the communication pathways between the endocrine and nervous system with the sex organs resulting in them not developing correctly during puberty. Usually this means some sort of malfunction in two endocrine glands located within the brain called the hypothalamus and the pituitary. Kallmann’s and its related conditions are secondary hypogonadism conditions.

There can be a wide number of reasons for hypogonadism so it is important to seek expert medical help. All the different conditions have different forms of treatment available.

Primary hypogonadism where previously normally functioning ovaries or testes stop functioning during life is far more common than the secondary hypogonadism seen in Kallmann's syndrome or HH.