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Kallmann syndrome (KS) is a genetic disorder that prevents a person from starting or fully completing puberty. If left untreated people with Kallmann syndrome will have poorly defined secondary sexual characteristics, show signs of hypogonadism, almost invariably be infertile and be at increased risk of developing osteoporosis.[1]
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Kallmann syndrome is a form of a group of conditions termed hypogonadotropic hypogonadism. Kallmann syndrome has an additional symptom of a total lack of sense of smell or a reduced sense of sense of smell which distinguishes it from other forms of hypogonadotropic hypogonadism.[1]
The underlying cause of the condition is a failure in the correct production or activity of the hormone normally produced by the hypothalamus called GnRH. This failure can lead to problems with the normal progression of puberty, failure of the reproductive cycle and hypogonadism. Hypogonadism is characterised by low levels of the sex hormones testosterone in males or oestrogen and progesterone in females. A range of other physical symptoms affecting the face, hands and skeletal system can also occur in some cases of Kallmann syndrome or hypogonadotropic hypogonadism. Diagnosis normally occurs during teenage years when puberty fails to start. Treatment for both males and females is normally required life long. Hormone replacement therapy (HRT) is the major form of treatment with the aim to replace the missing testosterone or oestrogen / progesterone. Specialised fertility treatments are also available.[2][3][4]
A 2011 study of the Finnish population produced an estimated incidence of 1 in 48,000 people overall, with 1 in 30,000 for males and 1 in 125,000 for females.[5] The condition is more commonly diagnosed in males than in females.[6] Kallmann syndrome was first described by name in a paper published in 1944 by Franz Josef Kallmann, a German-American geneticist.[7][8] The link between anosmia and hypogonadism had already been noted by the Spanish doctor Aureliano Maestre de San Juan in 1856.[9]
It is normally difficult to distinguish a case of KS / HH from a straightforward constitutional delay of puberty. However, if puberty has not started by either age 14 (girls) or 15 (boys) and one or more of the non-reproductie features mentioned belowe is present then a referral to reproductive endocrinologist might be advisable.[10]
The features of Kallmann syndrome (KS) and other forms of hypogonadotropic hypogonadism (HH) can be split into two different categories; "reproductive" and "non reproductive".[3][11][4][12][2]
- Failure to start or fully complete puberty in both men and women
- Lack of testicle development in men (size < 4 ml, whereas the normal range is between 12 and 25 ml)
- Primary amenorrhoea (failure to start menstruation)
- Poorly defined secondary sexual characteristics in both men and women.
- Micropenis in 5-10% of male cases
- Cryptorchidism (undescended testicles) at birth.
- Low levels of the gonadotropins LH and FSH
- Hypogonadism due to low levels of testosterone in men or oestrogen / progesterone in females
- Infertility
- Total lack of sense of smell (anosmia) or markedly reduced sense of smell (hyposmia). This is the defining feature of Kallmann syndrome; it is not seen in other cases of HH. Approximately 50% of HH cases occur with anosmia and can be termed as Kallmann syndrome.[2]
- Cleft palate, hare lip or other midline cranio-facial defects.[3]
- Neural hearing impairment[2]
- Absence of one of the kidneys (unilateral renal agenesis)[2]
- Skeletal defects including split hand/foot (ectrodactyly), shortened middle finger (metacarpal) or scoliosis[2]
- Manual synkinesis (mirror movements of hands)[2]
- Missing teeth (hypodontia)[2]
- Poor balance or coordination due to cerebral ataxia
- Eye movement abnormalities
The exact genetic nature of each particular case of KS / HH will determine which, if any, of the non-reproductive features will occur. The severity of the symptoms will also vary from case to case. Even family members will not show the same range or severity of symptoms.[2]
KS / HH is most often present from birth but adult onset versions are found in both males and females. The hypothalamic-pituitary-gonadal axis (HPG axis) functions normally at birth and well into adult life giving normal puberty and normal reproductive function. The HPG axis then either fails totally or is reduced to a very low level of GnRH release, in adult life with no obvious cause such as a pituitary tumour. This will lead to a fall in testosterone or oestrogen levels and infertility.
Functional hypothalamic amenorrhoea is seen in females where the HPG axis is suppressed in response to physical or psychological stress or malnutrition. It is reversible with the removal of the stressor.
Some cases of KS / HH appear to reverse during adult life where the HPG axis resumes its normal function and GnRH, LH, and FSH levels return to normal levels. This occurs in an estimated 10 to 20% of cases, primarily normosmic CHH cases rather than KS cases and only found in patients who have undergone some form of testosterone replacement therapy. It is only normally discovered when testicular volume increases while on testosterone treatment alone and testosterone levels return to normal when treatment is stopped. This type of KS/CHH rarely occurs in cases where males have had a history of un-descended testes.
Affected individuals with KS and other forms of HH are almost invariably born with normal sexual differentiation; i.e., they are physically male or female. This is due to the human chorionic gonadotrophin (hCG) produced by placenta at approximately 12 to 20 weeks gestation (pregnancy) which is normally unaffected by having KS or CHH.
People with KS/CHH lack the surge of GnRH, LH, and FSH that normally occurs between birth and six months of age. This surge is particularly important in infant boys as it helps with testicular descent into the scrotum. The surge of GnRH/LH/FSH in non KS/HH children gives detectable levels of testosterone in boys and oestrogen & progesterone in girls. The lack of this surge can sometimes be used as a diagnostic tool if KS/CHH is suspected in a newborn boy, but is not normally distinct enough for diagnosis in girls.[3]
Taken together, it is likely that testosterone has direct effects on bone quality via the androgen receptor as well as indirect effects via conversion to estrogen by aromatase. Bisphosphonates should be first-line therapy in the treatment of male hypogonadism-related osteoporosis, with the consideration for the addition of testosterone replacement therapy.
One possible side effect of having KS/CHH is the increased risk of developing secondary osteoporosis or osteopenia. Oestrogen (females) or testosterone (males) is essential for maintaining bone density.[16] Deficiency in either testosterone or oestrogen can increase the rate of bone resorption while at the same time slowing down the rate of bone formation. Overall this can lead to weakened, fragile bones which have a higher tendency to fracture.
Even a short time with low oestrogen or testosterone, as in cases of delayed diagnosis of KS/CHH can lead to an increased risk of developing osteoporosis but other risk factors are involved so the risk of developing it will vary from person to person.
People with KS/CHH should have a bone density scan at least every five years, even if they are on constant hormone replacement therapy. This interval will be shortened to three years if the patient is already in the at-risk zone (osteopenia) or yearly if the patient has osteoporosis already.
The bone density scan is known as a dual energy X-ray absorptiometry scan (DEXA or DXA scan). It is a very simple straightforward test, taking less than 15 minutes to perform. It involves taking a specialised X-ray picture of the spine and hips and measuring the bone mineral density and comparing the result to the average value for a young healthy adult in the general population.[17]
Adequate calcium levels, and probably more importantly vitamin D levels are essential for healthy bone density. Some patients with KS/CHH will have their levels checked and may be prescribed extra vitamin D tablets or injections to try to prevent the condition getting worse. The role of vitamin D for general overall health is under close scrutiny at the moment with some researchers claiming vitamin D deficiency is prevalent in many populations and can be linked to other disease states.
Some people with severe osteoporosis might be prescribed bisphosphonates to preserve bone mass. Exercise, especially weight bearing and resistance exercise, is known to reduce the risk of osteoporosis.
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In males with KS / CHH infertility is primarily due the lack of sperm production within the testes. Sperm production can be achieved through either the use of GnRH administered via a micro infusion pump or through the use of gonadotropin injections (hCG,FSH,hMG). The time taken to achieve adequate sperm production for natural conception will vary from person to person. If the pre treatment testes are very small and there has been a history of undescended testes it might take longer to achieve sperm production. In these cases assisted reproductive technology such as sperm retrieval using testicular sperm extraction (TESE) and / or intracytoplasmic sperm injection (ICSI) might be required.[27]
In females with KS / CHH infertility is primarily due to the lack of maturation of eggs located within the ovaries. Ovulation induction can be achieved either with pulsatile GnRH therapy or alternatively with gonadotropin injections (hCG,FSH,hMG) given at set intervals to trigger the maturation and release of the egg to allow for natural conception.[27]
The gonadotrophin deficiency in men and women with nCHH/KS is a cause of infertility resulting from failed gamete production and/or maturation (5-9). In men with CHH/KS, infertility is due to absent sperm production (5,6,27,28). However, spermatogenesis can be induced in most cases by either long-term pulsatile GnRH administration via a microinfusion pump, or by exogenous gonadotropin injections 5,6,27,28). A number of studies conducted over the past 30 years have clearly demonstrated that these treatments can be effective (5-9,27,28). In the most difficult cases (patients with very small testes and/or with cryptorchidism)(29,30), longer treatment may be required to conceive as well as use of assisted reproductive techniques (ART) i.e. microsurgical testicular sperm extraction (micro-TESE) and/or intracytoplasmic sperm injection (ICSI) (27,28,31,32).
[28] [28] [28] [28] [28] [28] [28]
Abnormalities in various genes have be shown to disrupt the ability of the hypothalamus to produce gonadotrophin releasing hormone GnRH which in turn causes the pituitary to fail to release sufficient levels of follicle-stimulating hormone (FSH) and luteinising hormone (LH). LH and FSH have a direct action on the testes in men and ovaries in women.[12]
Sixteen known gene defects have so far been shown to cause a disruption in GnRH production.[37] These gene defects can be split into two separate groups depending on their resluting action on the hypothalamus.
One group of gene defects disrupt the ability of the hypothalamus itself to produce or release GnRH, leading to a case of HH with an unaffected sense of smell, sometimes called normosmic hypogonadotrophic hypogonadism (nHH). The other major group of gene defects affect the migration of GnRH neurones into the hypothalmus during embryonic development. Since the GnRH neurones and olfactory neurones travel along the same pathways any impairment in GnRH neurone migration also prevents olfactory neurone migration leading to the anosmia or lack of sense of smell seen in Kallmann syndrome.
Table of known genes responsible for cases of Kallmann syndrome and other forms of hypogonadotropic hypogonadism. Listed are the estimated prevalence of cases caused by the specific gene, additional associated symptoms and the form of inheritance.[6][2] Between 35-45% of cases of KS / CHH have an unknown genetic cause.[26]
Prevalence (%) | OMIM | Name | Gene | Locus | Clinical features | Syndromes Associated | Inheritance pattern |
---|---|---|---|---|---|---|---|
5,[6] 5-10[2] | 308700 | KAL1 (ANOS1) | KAL1 | Xp22.3 | Anosmia. Bimanual synkinesis. Renal agenesis. | x-linked | |
10[6][2] | 147950 | KAL2 | FGFR1 | 8p11.23 | Cleft lip and / or cleft palate. Septo-optic dysplasia. Skeletal anomomalies. Bimanual synkinesis. Hand / foot malformations such as ectrodactyly. Combined pituitary hormone deficiency. | Hartsfield syndrome | Autosomal dominant |
6-16,[6] 5-10[2] | 146110 | GNRHR | GNRHR | 4q13.2 | Autosomal recessive | ||
6,[6] 5-10[2] | 612370 | CHD7 | CHD7 | 8q12.2 | Congenital hearing loss. Semicircular canal hypoplasia. | CHARGE syndrome | Autosomal dominant |
3-6,[6] <2[2] | 610628 | KAL4 | PROK2 | 3p13 | Autosomal recessive | ||
3-6,[6] 5[2] | 244200 | KAL3 | PROKR2 | 20p12.3 | Combined pituitary hormone deficiency. | Morning Glory syndrome | Autosomal recessive |
3,[6] 2-5[2] | 615267 | IL17RD | IL17RD | 3p14.3 | Congenital hearing loss. | Autosomal recessive | |
2,[6] 2-5[2] | 611584 | SOX10 | SOX10 | 22q13.1 | Congenital hearing loss. | Waardenburg syndrome | Autosomal dominant |
2,[6] <2[2] | 614842 | KISS1 | KiSS-1 | 1q32.1 | Autosomal recessive | ||
2,[6] <2[2] | 614837 | KISS1R (GPR54) | GPR54 | 19p13.3 | Autosomal recessive | ||
<2[2] | 612702 | FGF8 | FGF8 | 10q24.32 | Cleft lip and / or cleft palate. Skeletal anomomolies. Bimanual synkinesis. Combined pituitary hormone deficiency. | Autosomal dominant | |
<2,[6] 1 report[2] | 615270 | FGF17 | FGF17 | 8p21.3 | Dandy-Walker syndrome | Autosomal dominant | |
<2[6] | 164260 | LEP | LEP | 7q32.1 | Early onset of morbid obesity. | Autosomal recessive | |
<2[6] | 601007 | LEPR | LEPR | 1p31.3 | Early onset of morbid obesity. | Autosomal recessive | |
<2[6] | 162150 | PCSK1 | PCSK1 | 5q15 | Early onset of morbid obesity. | Autosomal recessive | |
Rare,[6] 1 report[2] | 616030 | FEZF1 | FEZF1 | 7q31.32 | Autosomal recessive | ||
Rare,[6] 1 report[2] | 616031 | CCDC141 | CCDC141 | 2q31.2 | Unknown | ||
Rare,[6] <2[2] | 614897 | SEMA3A | SEMA3A | 7q21.11 | Autosomal dominant | ||
1 report[2] | 608166 | SEMA3E | SEMA3E | 7q21.11 | CHARGE syndrome | Autosomal dominant | |
Rare[6] | 607961 | SEMA7A | SEMA7A | 15q24.1 | Autosomal dominant | ||
Rare,[6] <2[2] | 614880 | HS6ST1 | HS6ST1 | 2q14.3 | Cleft lip and / or cleft palate. Skeletal anomalies. | Autosomal dominant | |
Rare,[6] 1 report[2] | 614858 | WDR11 | WDR11 | 10q26.12 | Combined pituitary hormone deficiency. | Autosomal dominant | |
Rare[6] | 614838 | NELF (NSMF) | NELF | 9q34.3 | Autosomal dominant | ||
Rare[6] | 617351 | IGSF10 | IGSF10 | 3q24 | Autosomal dominant | ||
Rare,[6] <2[2] | 614841 | GNRH1 | GNRH1 | 8p21.2 | Autosomal recessive | ||
Rare,[6] <2[2] | 614839 | TAC3 | TAC3 | 12q3 | Autosomal recessive | ||
Rare,[6] 5[2] | 614840 | TACR3 | TACR3 | 4q24 | Autosomal recessive | ||
Rare[6] | 611744 | OTUD4 | OTUD4 | 4q31.21 | Cerebellar ataxia. | Gordon Holmes syndrome | Autosomal recessive |
Rare[6] | 609948 | RNF216 | RNF216 | 7p22.1 | Cerebellar ataxia. | Gordon Holmes syndrome | Autosomal recessive |
Rare[6] | 603197 | PNPLA6 | PNPLA6 | 19p13.2 | Cerebellar ataxia. | Gordon Holmes syndrome | Autosomal recessive |
1 report[2] | 109135 | AXL | AXL | 19q13.2 | Unknown | ||
Rare[6] | 612186 | DMXL2 | DMXL2 | 15q21.2 | Polyendocrine deficiencies and polyneuropathy. | Autosomal recessive | |
Rare[6] | 300473 | NR0B1 (DAX1) | NR0B1 | Xp21.2 | Adrenal hypoplasia. | x-linked | |
1 report[2] | 602748 | DUSP6 | DUSP6 | 12q21.33 | Autosomal dominant | ||
1 report[2] | 614366 | POLR3B | POLR3B | 12q23.3 | Autosomal recessive | ||
1 report[2] | 615266 | SPRY4 | SPRY4 | 5q31.3 | Autosomal dominant | ||
1 report[2] | 615271 | FLRT3 | FLRT3 | 20p12.1 | Autosomal dominant | ||
1 report[2] | 617264 | SRA1 | SRA1 | 19q13.33 | Unknown | ||
Rare[6] | 601802 | HESX1 | HESX1 | 3p14.3 | Septo-optic dysplasia. Combined pituitary hormone deficiency. | Autosomal recessive and dominant |
704 is consensus guidelines
Diagnosis of KS / CHH normal involves a range of clinical, biochemical and radiological tests to exclude other conditions that can cause similar symptoms.