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Kallmann syndrome – frequently asked questions. Part 2.

June 13, 2011

Is KS and HH hereditary?

Yes it can be, but the majority of cases still appear to be ‘sporadic’ or ‘isolated’. There are some types of KS and HH that are passed
down from generation to generation. The majority of cases arise with no apparent family history and appear to be sporadic. It must be noted that the terms sporadic and isolated can be a bit misleading as it is quite possible that a seemingly isolated case may just be the first occurrence of a hereditary type. This is why specialist advice is needed to try to determine what form of KS or HH an individual may have.

There are at least 4 different types of inherited KS and HH that are known about at present. The most widely known, and apparently the most common is x-linked Kallmann’s. This means that Kallmann’s is passed down through the generations on the X chromosome. This means that men are for more likely to develop x-linked Kallmann’s than women. Women tend to be carriers of
the x-linked type, i.e. they can pass it onto to anther generation without having the condition themselves.

Most people with KS / HH will not know the genetic origins of their condition so if fertility treatments are attempted it should be assumed there is a chance of passing on the condition but it is very difficult to be able to put a percentage to the chance of it occurring.

 What causes KS or HH?

KS and HH are classed as congenital disorders because they arise from the genetic code that causes each one of us to be individuals. The genetic code is contained in virtually every living cell and is the blue print or computer programme that is required to produce every part of an individual. Each person’s code is different but only varies very slightly to produce individual characteristics like body shape, eye colour and height. However sometimes an error occurs in the programme that causes a vital part of the body not to be formed or not to function properly. This can lead to a specific disease or disorder. Cystic fibrosis is an example of a very serious congenital disorder.

Kallmann’s in particular and possible a few other forms of HH are thought to arise because the cells of the hypothalamus gland, located deep within the brain,  that should release the correct hormone (GnRH or LHRH) to initiate puberty are absent. During the development of the brain from a foetus to a baby these cells have to migrate from another area of the brain. In Kallmann’s and some forms of HH this migration is blocked and the hypothalamus is formed without GnRH producing cells. It does however have all its other hormonal functions.

There are other situations where all the other hormones produced by the hypothalamus and pituitary is affected, along with the sex
hormones. This will cause a wide range of symptoms not just the developmental symptoms as seen in KS or HH. This is why it is important to consult an endocrinologist in order to determine how well the hypothalamus and pituitary glands are functioning.

These errors occur in very small sections of the genetic code called genes, which is where the term genetic disease comes from. There are tens of thousands of genes within the genetic code, more correctly called the genome. There are currently 8 genes in which errors have been found that can cause the inherited form of KS or HH. Some errors appear at random and are termed ‘isolated’. At present there is no one single gene defect that covers all cases of KS / HH, but this may change over time as more reasearch is done.

KS / HH are known as endocrine or pituitary conditions as the root of the problem lies with the pituitary and hypothalamus glands. For most people with KS / HH the cause of the condition is the failure of the hormone signals between these two glands which prevents puberty from starting or fully completing.

How is KS or HH diagnosed?

Unless there is a family history the peak age of diagnosis still appears to be in thee late teens or early 20’s. KS and HH are usually picked up because of absent puberty and all other possible causes have been eliminated. There are some physical features, other than absent pubertal growth that occur in cases of KS / HH. Not all the features will occur; it does depend on the type of HH.

Possible physical features:

Failure to enter puberty by the age of 15

Failure to begin periods in females

Lack of breast development in females

Lack of testicular growth in males

Lack of muscle bulk

Young appearance

Tall stature –above average arm span and height.

Lack of pubic and axillary hair.

Lack of smell (Kallmann’s only)

Cryptorchidism (un-descended testes at birth – either one or both)

Nerve deafness

Unilateral renal agenesis (absence of one of the kidneys)

‘Mirror’ movements of the hands or feet

Cleft palette / hare lip or other facial deformities

This is not an exhaustive list. The failure to go through puberty and the lack of smell are definitive characteristics. The other
features may or may not occur depending on each individual case, and may or may not be connected to Kallmann’s or HH.

Hormonal features:

Low levels of circulating testosterone / oestrogen / progesterone

Low levels of serum LH and FSH.

No sperm production.

A GP or local doctor can do some of these tests in the first instance. However specialist medical advice is need for a definite diagnosis and to rule out any other possible cause of delay of puberty.

Why do I appear to be so tall?

During puberty the bones, especially the long bones in the arms and legs grow to their maximum length and are then hardened by the deposition of calcium. The sex hormones, testosterone and oestrogen are required at puberty to ensure the ends of the bones get fused and harden to prevent further growth. If the hormones are not present or are at very low levels this hardening gets delayed and bone growth continues past its usual stage. The bones will stop growing eventually but the level of calcium
deposition will be less than normal and may make the bones weaker than normal.

Growth hormone makes the bones grow but testosterone or oestrogen is meant to ensure they don’t grow past their correct length at puberty and harden correctly. The lack of testosterone / oestrogen at puberty can leave people with above average height and an increased risk of having weak bones (osteoporosis)

 

Why do I lack a sense of smell?

In KS but not other forms of HH a person will not have a sense of smell. A first glance puberty and sense of smell may not go together. The part of the brain that is involved in the sense of smell is called the olfactory bulb. It just so happens that the olfactory bulb lies very close to the pituitary and hypothalamus glands within the brain.

The olfactory bulb is linked to the brain via a small bridge of tissue called the olfactory tract. For the hypothalamus to be fully
functional this tract must be present. In Kallmann’s this tract is missing or not fully formed. This means that there is no connection between the olfactory bulb and the brain so there is no sense of smell. The part of the hypothalamus that releases GnRH which initiates puberty also requires this olfactory tract to be present. If it is missing the hypothalamus can not release GnRH and hence puberty does not commence. In other forms of HH there are other reasons why the hypothalamus cannot release GnRH but the olfactory tract is present so the sense of smell is present.

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2 Comments
  1. What is nerve deafness?

    • Sensory nerve deafness is a symptom that is often found in cases of Kallmann syndrome or HH.

      It is where there is a problem in the development of the nerve that connects the ear to the brain so the person is left with a reduced level of hearing in one or both ears.

      There is nothing physically wrong with the ear itself, the problem lies between the connection between the inner ear and the brain.

      Some people with KS / HH will have reduced levels of hearing and may be required to wear hearing aids in one or both ears.

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