Testicular aplasia

Among the developmental anomalies of male genital organs with a normal karyotype (46, XY) is such a congenital defect of the genitals as testicular aplasia - the absence of one or both testicles 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.

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Epidemiology

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

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

Although, as experts note, when diagnosing unilateral cryptorchidism, out of 26% of cases of non-palpable testicle, aplasia (its absence) accounts for up to 10% of cases.

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Causes testicular aplasia

The main causes of testicular aplasia are rooted in disturbances in the ontogenesis of the external genitalia during the period of intrauterine development of the embryo and fetus.

When the defect is present on only one side – aplasia of the left testicle or aplasia of the right testicle – we are talking about monorchism or unilateral testicular agenesis. If both testicles are absent, then this is anorchia or agonadism.

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Risk factors

Experts cite such risk factors for testicular aplasia as gene mutations (in particular, the SRY gene), exposure of the expectant mother's body in the first or second month of pregnancy to radiation, electromagnetic radiation, mutagenic chemicals, alcohol and psychotropic substances, and certain medications (in particular, analgesics and hormonal agents).

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

This defect, like cryptorchidism (non-descending of the testicle into the scrotum), is observed in newborn boys born during significant prematurity.

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Pathogenesis

The pathogenesis of this anomaly of the 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 already in the 4th week in the mesonephros of the embryo (medial to the mesonephric ducts) the rudiments of the sex glands appear in the form of gonadal urogenital ridges, which have no sexual difference until the 8th week.

Only by the end of the second month of pregnancy does the embryo's set of chromosomes determine the differentiation of its sex. This is the Y-chromosome gene SRY, which codes the ontogenesis of the testes. Thanks to the activation of the protein transcription factor TDF (testis-determining factor), the male sex glands - the testes - begin to develop.

At the same time, after the 9th week of intrauterine development, the primary germ cells (gonocytes) of the fetus, under the influence of chorionic gonadotropin, begin to secrete androgenic steroids (androstenedione) and the male sex hormone testosterone. With insufficient inducing activity of TDF, testosterone is produced less than normal, which leads to testicular regression and anomalies in the formation of the gonads - testicular aplasia (monorchism or anorchia).

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Symptoms testicular aplasia

If one or both testicles are absent from the scrotum, the symptoms of testicular aplasia – monorchism or anorchia – are immediately visible.

And the first signs that a neonatologist notes when examining a newborn are the presence of one testicle in the absence of the second - if testicular agenesis is unilateral. In this case, the size of the scrotum (scrotum) on the side of aplasia is significantly smaller.

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

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Complications and consequences

However, this is not the case in all cases, and if the level of testosterone synthesized by one testicle is too low, then adolescent boys may have such consequences and complications of testicular aplasia as primary hypogonadism: delayed development of secondary sexual characteristics, disorders of skeletal and muscular formation, gynecomastia, accumulation of excess fat deposits. As a result, men do not have sexual and reproductive capabilities.

In anorchia – the absence of both testicles – the severity of hypogonadism, in particular the appearance of signs of eunuchoidism, depends on the stage of intrauterine development at which disturbances in the formation of the genitals in the fetus occurred.

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Diagnostics testicular aplasia

Testicular aplasia is usually diagnosed in newborn boys during a routine examination in the maternity hospital. According to statistics, in the presence of a testicular anomaly, an experienced doctor can detect cryptorchidism by palpation in 70% of cases, in which the testicle does not descend into the scrotum due to retention in the inguinal canal or abdominal cavity.

In the remaining 30% of cases, the testicle cannot be palpated, and the task is to confirm the absence of testicles - testicular aplasia - or to determine the location of a viable testicle that has not descended into the scrotum in a timely manner.

Tests to detect testicular aplasia include blood tests for hormones such as testosterone, androstenedione, LH (luteinizing hormone), FSH (follicle-stimulating hormone), and AMH (anti-Müllerian hormone). Newborn boys with bilateral non-palpable testicles should have their chromosome complement (karyotype) tested, blood tests for 17-hydroxyprogesterone levels, and be evaluated for life-threatening congenital adrenal hyperplasia. This testing is necessary because a boy with bilateral cryptorchidism or bilateral testicular aplasia may be mistaken for a child with a 46,XX karyotype and adrenal hyperplasia.

Instrumental diagnostics are carried out using testicular scintigraphy, ultrasound of the abdominal organs, CT or MRI of the inguinal and abdominal region.

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Differential diagnosis

In this case, differential diagnostics are necessary to detect possible cryptorchidism with abdominal retention of the testicle. To detect testicular retention - in all unilateral and bilateral non-palpable cases - diagnostic laparoscopy is used, which with absolute accuracy confirms the absence of testicles in their aplasia.

Treatment testicular aplasia

Today, treatment of testicular aplasia consists of the use of hormonal drugs that compensate for the deficiency of endogenous testosterone. For boys, such treatment begins in the prepubertal period.

The drug of the androgen group Testosterone propionate (Androlin, Andronate, Gomosterone, Testenate, Omnadren 250, Sustanon) administered subcutaneously or intramuscularly is prescribed in an individually determined dosage - once a day or every other day. The duration of use of this drug depends on the body's reaction and effectiveness.

The synthetic analogue of testosterone Methyltestosterone (Androral, Gormal, Madiol, Metandren, Oraviron, Testoral) is prescribed in long courses of 20-30 mg per day (once every two days or every day).

Andriol (40 mg capsules) is taken orally one capsule three times a day for 24 hours. After a 21-day course, the dose is reduced to a single dose for a longer period of time.

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

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

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

Prevention

Prevention of birth defects that occur during intrauterine development is problematic, and experts advise to protect yourself from infections during pregnancy and not to take any medications without a doctor's prescription.

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Forecast

The prognosis for unilateral testicular aplasia is more optimistic regarding the functioning of the reproductive system, since with anorchia even replacement therapy is not able to fully restore the functions of the missing testicles.

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