Aplasia of the testis

Among the anomalies in the development of male genital organs in a normal karyotype (46, XY) is a congenital defect of the genitals such as testicular aplasia - the absence of one or both testes in the scrotum due to agenesis, that is, because they are not formed. The code for this pathology according to ICD-10 is Q55.0.

[1], [2], [3], [4], [5]

Epidemiology

Statistics show that unilateral testicular aplasia occurs in 15-20 full-term newborn boys for every 100,000 male infants. A bilateral aplasia - in three to five.

According to the American Urological Association, if the incidence of such a testicular defect as cryptorchidism in the general population of full-term newborn boys is on average 3.2%, then left testicular aplasia or right testis aplasia is 20 times less common.

Although, as experts note, in the diagnosis of unilateral cryptorchidism, out of 26% of cases of non-palpable testis on aplasia (its absence) account for up to 10% of cases.

[6], [7], [8], [9], [10]

Causes of the aplasia of the testicle

The main causes of testicular aplasia are found in violations of the ontogeny of the external genital organs during the fetal development of the embryo and fetus.

When the defect is only on one side - aplasia of the left testicle or aplasia of the right testicle - it is a question of monarchism or unilateral testicular agenesis. If both testicles are absent, then this is anarchy or agonadism.

[11], [12], [13], [14]

Risk factors

Experts call such risk factors for testicular aplasia as mutations of genes (in particular, the SRY gene), the impact on the organism of the expectant mother in the first-second month of pregnancy of radiation, electromagnetic radiation, mutagenic chemicals, alcohol and psychotropic substances, certain medications (in particular, analgesics and hormonal agents).

Anomalies of the fetus's external genital organs may be a consequence of endocrine pathologies of pregnant women, hormonal disorders, excess weight, and infectious diseases.

This defect, like cryptorchidism (undescended testicle in the scrotum), is observed in newborn boys born with a significant premature pregnancy.

[15], [16], [17], [18], [19]

Pathogenesis

The pathogenesis of this abnormality of male reproductive organs is associated with the peculiarities of their formation at the end of the embryonic period (from the 7th week of pregnancy). Although even at the 4th week in the mesonephros of the embryo (medial to the mesophilic ducts) germs of the genital glands appear in the form of gonadal urogenital ridges that do not have sex differences until the 8th week.

Only by the end of the second month of pregnancy, the chromosome set in the embryo determines the differentiation of its sex. This is the Y-chromosome SRY gene, which codes for the ontogeny of the testes. Thanks to the activation of the protein transcription factor TDF (testis-determining factor) and male gonads - testes begin to develop.

In this case, after the 9th week of intrauterine development, the primary sex cells (gonocytes) of the fetus under the influence of the chorionic gonadotropin begin to secrete androgenic steroids (androstenedione) and the male sex hormone testosterone. With insufficient inducing activity, TDF testosterone is produced less than normal, which leads to testicular regression and anomalies in the formation of gonadal aplasia (monarchism or anarchy).

[20], [21]

Symptoms of the aplasia of the testicle

In the absence of one or both testes in the scrotum, the symptoms of testicular aplasia - monarchism or anarchy - are immediately apparent.

And the first signs, which the neonatologist notes when examining the newborn, is the presence of one testicle in the absence of the second - if testicular agenesis is one-sided. In this case, the size of the scrotum (scrotum) from the side of the aplasia is much smaller.

In the future, the symptoms of testicular aplasia may be manifested depending on the degree of compensatory possibilities of the testicle. When it functions normally, testosterone is enough, and the boy develops without any deviations, and even problems with conception in men with compensated monarchism do not arise.

[22]

Complications and consequences

However, this is not always the case, and if the level of testosterone synthesized by one testicle is too low, then adolescent boys may have consequences and complications of testicular aplasia, such as primary hypogonadism : delay in the development of secondary sexual characteristics, disruption of the formation of the skeleton and musculature, gynecomastia , the accumulation of excess fatty deposits. As a result, men do not have sexual and reproductive capabilities.

In an anarchy - the absence of both testicles - the severity of hypogonadism, in particular the appearance of signs of eunuchoidism, depends on the stage of intrauterine development in which the genitalia of the fetus were disturbed.

[23], [24],

Diagnostics of the aplasia of the testicle

Usually, the diagnosis of testicular aplasia is performed in newborn boys at a standard examination in the maternity hospital. According to statistics, in the presence of a testicular anomaly, an experienced physician by palpation in 70% of cases reveals cryptorchidism, in which the testicle does not descend into the scrotum due to retention (delay) in the inguinal canal or in the abdominal cavity.

In the remaining 30% of cases, the testicle is not probed, and the task is to confirm the absence of testes - testicular aplasia - or to locate a viable testicle that did not descend in time to the scrotum.

Analyzes for the detection of testicular aplasia include a study of blood levels of hormones such as testosterone, androstenedione, LH (luteinizing hormone), FSH (follicle stimulating hormone), AMG (anti-Muller's hormone). Newborn boys with bilateral non-palpable testicles should be tested for the determination of a set of chromosomes (karyotype) and take a blood test for the level of 17-hydroxyprogesterone, and also examine for life-threatening congenital dysfunction of the adrenal cortex. The need for such an examination is due to the fact that a boy with bilateral cryptorchidism or bilateral testicular aplasia can be mistaken for a child with a karyotype of 46, XX and hyperplasia of the adrenal cortex.

Instrumental diagnostics is carried out using testicular scintigraphy, ultrasonography of the abdominal cavity organs, CT or MRI of the inguinal and abdominal region.

[25], [26],

Differential diagnosis

In this case, differential diagnosis is necessary to identify possible cryptorchidism in abdominal testicular retention. For detection of testicle retention - for all unilateral and bilateral non-palpable cases - diagnostic laparoscopy is used, which with absolute accuracy confirms the absence of testicles during their aplasia.

Treatment of the aplasia of the testicle

To date, treatment of testicular aplasia consists of the use of hormonal drugs that compensate for the deficiency of endogenous testosterone. Boys such treatment begin in the prepubertal period.

Introduced subcutaneously or intramuscularly a preparation of the androgen group Testosterone propionate (Androlin, Andronat, Homosterone, Testanate, Omnadren 250, Sustanon) is administered in an individually defined dosage - once a day or every other day. The duration of use of this drug depends on the body's response and effectiveness.

Synthetic analogue of testosterone Methyltestosterone (Androlal, Gormal, Madiol, Methandren, Oraviron, Testol) is prescribed by long courses of 20-30 mg per day (every two days or every day).

Andriol (capsules 40 mg each) take one capsule three times a day during the day. After a 21-day course, the dose is reduced to a single dose for a longer time.

Mesterolone (Proviron) - a derivative of 5-androstanone - in tablets of 25 mg, doctors prescribe to take one tablet from one to three times a day.

All presented drugs can give such side effects as dizziness, nausea, muscle pain, acne, fluid retention in the body and salts, increased blood pressure, an increase in the number of red blood cells in the blood (increasing blood viscosity and fraught with blood clots in the blood vessels).

At the same age, with aplasia of the testicle, cosmetic surgery can be performed with the implantation of a silicone prosthesis into the scrotum.

Prevention

Prevention of a congenital defect that occurs during intrauterine development is problematic, and experts advise that during pregnancy, be careful of infections and not take any medications without prescribing a doctor.

[27], [28], [29], [30], [31], [32]

Forecast

The prognosis for unilateral testicular aplasia is more optimistic regarding the functioning of the reproductive system, since in anarchy even substitution therapy is not able to fully restore the function of missing testes.

[33]