DYSGENESIS OF GONADS

From Big Medical Encyclopedia

DYSGENESIS OF GONADS (grech, dys-+ genesis origin; grech, gone the birth, a seed + ad[en] of iron) — the collective concept including group of the diseases connected with the disturbances of embryonic development of gonads caused by aberation (gonosomny) quantitative or structural chromosomes, genovariations or embriotoksichesky factors.

Etiology Of, as well as the majority of the congenital anomalies caused by genetic and embriotoksichesky factors it is not clear.

Pathogeny

Pathogeny: chromosomal anomalies in the form of change of normal number of gonosomes or structure of one of them can arise at different stages of an early embryogenesis and cause disturbance of a sexual differentiation. The gonad demands for the development of two gonosomes (XX — an ovary, XY — a small egg). At a karyotype of X0, a mosaic of X0/XY or deformation of one X-chromosome the agenesia of the gonads taking a form of an undifferentiated gonadalny tyazh, sometimes with presence at it of underdeveloped ovarian or testicular elements is typical. The agenesia of gonads can be followed by disturbances of somatic development and low-tallness — Shereshevsky's syndrome — Turner (see. Turner syndrome ) or to proceed without somatic anomalies — «pure», or «true», an agenesia; the form D. of can be found in the same individual disgeneticheskiya of testicles on one party and undifferentiated tyazh on another — mixed, or asymmetric. Assume that the embryonal small egg works productively or two nonsteroid incretions, according to the derivatives of a mezonefralny (volfov) channel causing development allocate: epididymis, deferent duct, seed bubbles and reduction of derivatives of a paramezonefralny (myullerov) channel: uterus, uterine tubes, upper part of a vagina. Disturbance of embryonal function of testicles slows down development men's and involution of female generative organs; further defect of a steroidogenesis in testicles leads to development of an eunuchoid form of a dysgenesis of testicles (see. Pseudohermaphroditism ). This disease, also as a «true» agenesia of gonads, can develop without explicit chromosomal anomaly. During puberty increase of androgenic activity of disgenetichesky testicles with strengthening is possible virilescences (see) that leads to development of an androidny form D. of. In addition to above-stated a wedge, forms, the «steroid» form D. of at men is described (as Shereshevsky's syndrome — Turner), it is preferential with a karyotype 46,XY/45,X. At a karyotype of XXY, XY/XXY, XXYY, etc. the gonad is differentiated in a small egg and men's generative organs form. However excess of genetic material (excess chromosomes) leads to the dysgenesis of seed tubules which is shown in the pubertal period Klaynfelter's syndrome (see. Klaynfeltera syndrome ). Late manifestation of D. of is peculiar also to patients with chromosomal complement of XXX when the atrophy of an ovary comes in youth. As well as at other chromosomal anomalies, excess of genetic material often conducts to mental retardation.

The exact statistics of D. of does not exist, it is based on studying of separate chromosomal anomalies at persons with the changes found at mass inspection of the population sex chromatin (see). Frequency of chromosomal anomalies at newborn girls makes 0,15% (0,13% — with two sex chromatins; 0,02% — without sex chromatin). Newborns have a frequency is 45, X individuals — 0,04%, 47,XXY — 0,13%. At primary amenorrhea chromosomal anomalies meet in 40% of cases. At an azoospermism and the expressed oligospermatism the sex chromatin is found in men in 20% of cases.

By the pathogenetic principle allocate three main forms of inborn disturbances of a sexual differentiation: agenesia of gonads, ovarian and testicular D. of.

Preservation in one organism of elements of male and female gonads with their arrangement separately from two parties or jointly in both gonads (ovotestis) is observed at true hermaphroditism (see).

A clinical picture

Patients with a «pure» agenesia of gonads, irrespective of the available chromosomal complement (46,XX; 46, XY; mosaics with existence of a clone 45, X), phenotypical are women of high growth with eunuchoid proportions of a skeleton, an underdevelopment or lack of secondary sexual characteristics, female type of a structure of infantile outside genitals, an underdeveloped uterus, primary amenorrhea. Treatment by estrogen with imitation of female sexual cycles leads to feminization, development of secondary female sexual characters, emergence of the induced periods, however these patients remain sterile.

The ovarian dysgenesis is characterized by disturbance of formation of female generative organs and secondary sexual characteristics. At the same time at patients primary amenorrhea, opso-and an oligomenorrhea, anovulation is observed. One of rare options of dysfunctions of ovaries is after menarche and sharply shortened (sometimes up to 3 — 5 years) the period of cycling activity of ovaries. During this period approach of pregnancy is possible. The most frequent chromosomal options at an ovarian dysgenesis are mosaicism 45X/46XX and structural defects of X-chromosome. Treatment — a cyclic estrogenoterapiya, sometimes in combination with progestins.

Treatment

Treatment is defined by a clinical form of a disease. Correction of a floor (hormonal and surgical) shall be carried out taking into account psychosexual orientation and anatomo-fiziol, features of a reproductive system of the patient. Treatment of infertility is unpromising.

Disgenetichesky gonads (especially intraperitoneally the located testicles) tend to tumoral regeneration that demands onkol, vigilances.


Bibliography: Davidenkova E. F., the Berlin D. K. and Thousands nu to S. F. Clinical syndromes at anomalies of gonosomes, L., 1973; Fundamentals of cytogenetics of the person, under the editorship of A. A. Prokofieva-Belgovskaya, M., 1969; Teter E. Hormonal disturbances at men and women, the lane with polsk., Warsaw, 1968; Overzier C. Die Inter-sexualitat, Stuttgart, 1961; Z a b e 1 R. Chromosomenstudien bei Intersexua litat, Jena, 1966.

H. A. Zarubina.

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