Kallmann Syndrome (KS), also known as Maestre-Kallmann-Morsier Syndrome, is a genetic disease associated with hypogonadotropic hypogonadism, and smell disorders, including anosmia and hyposmia.
The disease can occur in both males and females, although it is more frequent in men. The prevalence of Kallmann Syndrome is 1 out of 8,000 males, and 1 out of 40,000 females.
Because KS affects the whole hypothalamic pituitary adrenal (HPA) axis and sex hormone production, it it considered to be a cause of infertility.
The different sections of this article have been assembled into the following table of contents.
Definition & causes
The German psychiatrist Franz Josef Kallmann (1897-1965) described and characterized this genetic disorder as a hereditary condition under the name Kallmann Syndrome (KS).
KS has a genetic origin and, as such, based on the type of mutation, it can have an autosomal dominant, autosomal recessive, or linked to X-chromosome inheritance.
People with KS lack the surge of GnRH (gonadotropin-releasing hormone) due to a failure during embryonic development.
Particularly, it is due to an error in the migration of hypothalamic neurons in charge of GnRH synthesis from the olfactory epithelium to the hypothalamic area of the brain.
GnRH is one of the hormones in charge of the hypothalamic pituitary adrenal (HPA) axis. When the hypothalamus releases GnRH, the hypophysis is stimulated to produce the hormones FSH and LH.
Simultaneously, FSH and LH are responsible for the regulation of sexual development in males and females.
Due to hypogonadotropic hypogonadism (HH) caused by KS, hence the common abbreviation KS-HH, people affected by it have an incomplete development of the reproductive system, along with a lack of sexual development.
As a result, both men and women will have poorly-defined secondary sexual characteristics when they reach puberty, aside from infertility issues.
The following are the most important signs and symptoms of Kallmann Syndrome in both sexes:
Based on age and the development phase the male finds himself in, it is possible to detect different alterations associated with KS.
For example, during childhood, having a micropenis and cryptorchidism can lead parents to suspect that their son may have this disorder.
After puberty, when the person reaches adulthood, men affected by KS will have a phenotype that is related to hypogonadism, along with a lack of testosterone:
- Reduced bone density and muscle mass
- Small testicular volume
- Erectile dysfunction
- Decreased libido
- Oligospermia or azoospermia
Moreover, adult men affected by KS typically look like teenagers, since some characteristics of childhood continue in their adulthood.
Common symptoms of KS in females are primary amenorrhea and an incomplete or absent development of the breasts during puberty.
Due to the lack of female sex hormones, such as estrogens, these women have anovulatory cycles (i.e. no egg is released). In other words, they have infertility problems.
A symptom of KS that is common in both sexes is, as explained above, the partial or total absence of the sense of smell, due to an incomplete development of the olfactive bulbs.
Also, although less frequently, affected individuals may have the following alterations as well:
- Renal disorders, like unilateral renal agenesis (URA)
- Moderate mental retardation
- Hearing loss
- Involuntary hand and/or eyeball movements
- Cleft palate
- Cleft lip
To determine whether someone actually suffers from KS, different diagnostic methods may be used:
- Hormone assessment
- FSH and LH hormones are measured, along with sex hormones, as testosterone and estrogens.
- Olfactory test
- The sense of smell is evaluated qualitatively and quantitatively. The olfactory bulbs can be seen via MRI.
- Clinical signs of hypogonadism
- Lack of secondary sexual characteristics, including amenorrhea, erectile dysfunction, loss of sex drive, etc.
- Genetic screening
- To identify the exact mutation that causes the disease.
The treatment of Kallmann Syndrome aims to achieve pubertal feminization or virilization in patients.
To this end, a hormonal replacement therapy is essential to be able to develop and maintain the secondary sexual characteristics. As for males, some examples are: body hair growth, deeper voice, muscle and bone development… In the case of women, the goal is to promote breast growth, have normal menstrual periods, pubic hair, etc.
Broadly speaking, KS patients typically require lifelong treatment.
When a person that suffers from KS wants to have children, hormone treatment should be changed in order for fertility to be restored. What follows are some recommended treatments based on gender:
- Males with KS
- Repeated GnRH injections promote spermatogenesis. Thus, sperm are expected to be detectable within 3 months. Another option is to combine hCG injections with FSH, since it increases the concentration of intratesticular testosterone.
- Females with KS
- Hormone therapy is administered in order to stimulate the ovaries mildly. Then, timed intercourse is recommended.
Should pregnancy not take place with any of these treatment options, or in case there exist more serious infertility issues, the couple might have no alternative but to undergo intrauterine insemination (IUI) or in vitro fertilization (IVF) to become parents.
To perform a PGD, one should undergo IVF as the main treatment. If you are looking for a clinic to get started, we recommend that you generate your individual Fertility Report now. It is a useful, simple tool that, in just 3 steps, will give you a list of the clinics that have passed our rigorous selection process. You will receive an email in your inbox with a report that contains tips and recommendations to get started.
Finally, as regards the recovery of the sense of smell, unfortunately there exists no cure or treatment nowadays.
FAQs from users
What distinguishes Kallmann Syndrome from other genetic diseases?
Kallmann Syndrome (KS) is a type of hypogonadotropic hypogonadism that occurs at birth, since it has a genetic and hereditary origin. However, it is also possible that the mutations that cause this disorder arise de novo.
Individuals affected by KS have an inadequate development of secondary sexual characteristics when they reach puberty, resulting in infertility during adulthood.
On the other hand, KS alters the sense of smell, causing disorders like anosmia and hyposmia.
What genes cause Kallmann Syndrome?
There exist several genetic mutations of different types of inheritance that can cause someone to develop Kallmann Syndrome:
- Sex-linked inheritance: KAL1 (Xp22.32)
- Autosomal dominant inheritance: FGFR1 (8p12), FGF8 (10q25-q26), CHD7 (8q12.2), and SOX10 (22q13.1)
- Autosomal recessive inheritance: PROKR2 (20p12.3), and PROK2 (3p21.1)
Depending on the mutation and gene affected, carriers of Kallmann Syndrome have no choice but to conceive using reproductive technologies in order to prevent the transmission of this genet to offspring.
Suggested for you
As explained earlier, Kallmann Syndrome is a genetic disease that can be inherited by offspring. To learn more about the different types of inheritance and their risk of transmission, continue reading here: What Genetic Diseases Can PGD Test for?
To get a much deeper insight on Kallmann Syndrome, it is crucial that one is familiar with the wide range of hormones that play a role in the organism of males and females. Recommended for you: Male & Female Sex Hormones – Definition & Functions.
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Freitas P, Carvalho S, Ribeiro F, Marnoto D, Martins F. Neuroradiology of Kallmann’s syndrome. Acta Med Port 2001;14:123-6.
Kallmann FJ, Schoenfeld WA, Barrera SE. The genetic aspects of primary eunuchoidism. Am J Ment Defic 1944;48:203-6.
Moorman JR, Crain B, Osborne D. Kallmann’s syndrome with associated cardiovascular and intracranial abnormalities. Am J Med 1984;77: 369-72.
Munez A, Dieguez E. A plea for proper recognition: The syndrome of Maestre de San Juan-Kallman. Am J Neuroradiol 1997;18:1395-6.
Seminara SB, Hayes FJ, Crowley WF Jr. Gonadotropin-releasing hormone deficiency in the human (idiopathic hypogonadotropic hypogonadism and Kallmann’s syndrome): pathophysiological and genetic considerations. Endocr Rev 1998;19:521–39
Stern Y, Egelhoff J, Shott SR. Imaging quiz. Absence of the olfactory bulb and tracts consistent with Kallmann syndrome. Arch Otolaryngol Head Neck Surg 1998;124:342-3.
Truwit CL, Barkovich AJ, Grumbach MM, Martini JJ. MR imaging of Kallmann Syndrome: A Genetic Disorder of neuronal migration affecting the Olfactory and Genital systems. Am J Neuroradiol 1993;14:827-38.