Congenital hypothyroidism – a complex of the clinical and laboratory manifestations arising at the child since the birth at insufficiency of hormones of a thyroid gland or immunity to them tropny bodies. Symptoms include lag in psychophysical development, miksedy, trophic violations of skin and its appendages, oppression of work of heart, decrease in the main exchange. Diagnostics is based on characteristic clinic, data of radiodiagnosis, ultrasonography of a thyroid gland, the ECG, laboratory researches, including measurements of tireotropny hormone and a tiroksin in blood plasma. Treatment means lifelong replacement therapy by artificial analogs of hormones of a thyroid gland.
The congenital hypothyroidism is the polietiologichesky disease which is characterized by clinical manifestations of insufficiency of a thyroid gland. Is the most widespread endocrine pathology in pediatrics. Most often the disease arises against the background of changes directly in a thyroid gland, is result of pathology of gipotalamo-hypophysial system or a defective structure of the receptor office of tropny bodies less often. In 90% of cases has sporadic character. Incidence – 1:3,7-4 thousand newborns in Europe and the USA, in Japan – 1:6-7 thousand. The female is ill 2-2,5 times more often than men's. The first screening tests on a congenital hypothyroidism were executed in 1973 by Canadians of J. Dussault, S. of Laberge. At the moment neonatal screening is carried out for the purpose of the most bystry diagnosis and if necessary - performing timely treatment.
Reasons of a congenital hypothyroidism
In 80-90% of cases there is primary form of a congenital hypothyroidism. The reasons – anomalies of development of a thyroid gland, most often – an allotopia in zagrudinny or hypoglossal space, are more rare – a hypoplasia, . Autoimmune and infectious diseases of mother, toxic influence of medicines, chemical means, radiation exposure, insufficiency of iodine can act as risk factors during pregnancy. About 2% of cases of malformations of gland – hereditary forms. Their main reason – mutations in genes of TITF1, TITF2, FOXE1, PAX8. As a rule, the genetic caused forms accompany other anomalies of development: congenital heart diseases, "a wolf mouth", etc.
From 5 to 10% of children with a congenital hypothyroidism have violations of synthesis, allocation or interaction of hormones of a thyroid gland. Transfer, as a rule, happens on autosomno-recessive type. The most frequent options – defects of an organifikation of iodine and tireoidny hormones (frequency – 1:40000), Pendred's syndrome (1:50000). Other forms meet extremely seldom.
About 5% of all cases of a congenital hypothyroidism – central (secondary or tertiary) forms. The most widespread option – the combined deficiency of hormones of an adenogipofiz, including TTG. The isolated deficiency meets seldom. The reasons of defeat of gipotalamo-hypophysial system – anomaly of development of a brain, a cyst, malignant and benign tumors, a patrimonial trauma of newborns, asphyxia at the time of delivery, it is rare – a hypophysis aplaziya.
The anomaly of structure of receptors in target organs caused by gene mutations can be the cause of development of clinical symptoms of a hypothyroidism. The impossibility of interaction of enough hormones with receptors of tropny fabrics provokes development of a so-called "syndrome of resistance". As a rule, it is the hereditary pathology which is transmitted on autosomno-prepotent type. At it the TTG level in blood plasma normal, T3 and T4 – in repartitions of norm or are moderately increased.
Classification of a congenital hypothyroidism
The congenital hypothyroidism has several classifications which are based on localization of violation, weight of symptoms and level of a tiroksin, compensation against the background of treatment and duration of a disease. By origin diseases allocate the following forms of a hypothyroidism:
- Primary, or tireogenny. Pathological changes arise directly in tissues of a thyroid gland.
- Secondary. Violations of work of an adenogipofiz at which there is a deficiency of synthesis of tireotropny hormone (TTG) develop.
- Tertiary. The insufficiency of a thyroid gland arising at deficiency of one of hypothalamus hormones – a tiroliberin. Together with a secondary form treats the central hypothyroidisms.
- Peripheral. Insufficiency of effect of hormones is caused by defect or lack of receptors in tropny fabrics or violation of conversion of a tiroksin (T4) in (T3).
On degree of expressiveness of clinical symptoms and the T4 level in plasma the hypothyroidism can be latent, manifest and complicated. The latent, or subclinical hypothyroidism is characterized by the normal T4 level against the background of increase in TTG. Clinical manifestations do not arise or they are not specific and hardly noticeable. At a manifest form against the background of high concentration of TTG the T4 level is a little reduced. The classical clinical picture of a hypothyroidism develops. The complicated hypothyroidism proceeds with the TTG high level, sharp deficiency of T4. Besides heavy degree of a hypothyroidism there are violations of other bodies and systems: heart failure, poliserozit, cretinism, a coma, is rare – hypophysis adenoma.
Depending on efficiency of treatment allocate a congenital hypothyroidism:
- compensated - against the background of the carried-out treatment of the phenomenon of a hypothyroidism disappear, concentration of TTG, T3, T4 in blood plasma – within norm;
- dekompensirovanny - even against the background of adequate treatment there are clinical and laboratory manifestations of a hypothyroidism.
On duration the congenital hypothyroidism is divided on:
- tranzitorny - a disease develops against the background of influence of antibodies of mother to the child's TTG. Duration – from 7 days to 1 month.
- permanent - demands performing lifelong replacement therapy.
Symptoms of a congenital hypothyroidism
Depending on a form and severity of violations the first signs of primary congenital hypothyroidism can demonstrate at different age. The sharp hypoplasia or an aplaziya of gland is shown in the first 7 days of life of the child. The allotopia or a weak hypoplasia can cause clinical manifestations aged from 2 up to 6 years.
Primary signs indicating a congenital hypothyroidism: the child's weight at the birth over 4 kg; immaturity at full-term or perenoshenny (more than 40 weeks) pregnancies; overdue otkhozhdeniye of mekonialny masses; long jaundice of newborns; dispepsichesky phenomena; slow increase of body weight; apathy; makroglossiya; meteorizm and locks; muscular weakness; hyporeflection; cyanosis and episodes during feeding. Integuments of the child cold, arise hypostases of extremities and genitals. The increased fontanels, not union of seams of bones of a skull, a dysplasia of coxofemoral joints are often observed. Breastfeeding is capable to reduce expressiveness of clinical manifestations of a hypothyroidism.
Primary congenital hypothyroidism develops step by step. The pronounced clinic is observed at the age of 3-6 months. There is a miksedema. The integuments condensed, icteric-gray, dry. Sweating is sharply reduced. The atrophy of nail plates and hair develops. Child's voice low, hoarse and rough. There is a lag in psychomotor and physical development, teeth are cut through and replaced with a delay. At further development intellectual backwardness is observed. It is shown by scarcity of a lexicon and decrease in intelligence which is inclined to progressing up to mental retardation.
The central congenital hypothyroidism has an indistinct clinical picture. It is often combined with anomalies of a facial skull ("cleft lip", "a wolf mouth") and insufficiency of other hormones of a hypophysis (somatotropny, lyuteiniziruyushchy and follikulostimuliruyushchy) with symptomatology characteristic for this purpose.
Diagnostics of a congenital hypothyroidism
Diagnostics of a congenital hypothyroidism includes collecting anamnestichesky data, objective inspection of the child by the pediatrician or neonatology, tool researches, the general and specific laboratory tests. In the anamnesis it is possible to reveal the contributing factors – the burdened heredity, diseases of mother during pregnancy, violation of food, use of obstetric grants at the time of delivery and so forth. At fizikalny inspection of the child decrease ChSS, AD, a moderate hypothermia, a hyporeflection, lag in development comes to light.
On the roentgenogram of extremities define lateness and violation of sequence of formation of kernels of ossification, their asymmetry and a specific sign – epifizarny . On the ECG – sinusovy bradycardia, decrease in amplitude of teeth, expansion of the QRS complex. Ultrasonography of a thyroid gland allows to reveal an allotopia, a hypoplasia or absence of this body.
In OAK – normokhromny anemia. In biochemical blood test increase in lipoproteid and cholesterol comes to light. At suspicion on the central origin of a hypothyroidism it is carried out by hypophysis KT and MPT. Specific laboratory tests – measurement of the T4 and TTG level in blood plasma. These tests are used as neonatal screening. Depending on a form of a hypothyroidism of concentration of these hormones in blood can be increased or lowered. Seldom apply a molecular and genetic research for the purpose of identification of a mutation of genes.
Treatment of a congenital hypothyroidism
Treatment of a congenital hypothyroidism begins immediately with the moment of diagnosis and continues for life. Choice medicine – L-tiroksin. This means is a synthetic analog of hormones of a thyroid gland and is used as replacement therapy. The dosage is selected individually. If necessary medicine can be mixed with breast milk. Efficiency of the carried-out treatment is estimated on the TTG and T4 level at blood, to disappearance of symptoms of a hypothyroidism. If necessary polyvitaminic complexes, symptomatic medicines are in addition appointed.
The forecast at a congenital hypothyroidism depends on adequacy and timeliness of treatment. At early diagnostics and in time the begun therapy, normalization of the TTG and T4 level – the forecast for psychophysical development favorable. In the absence of treatment for the first 3-6 months of life the forecast doubtful even at the correct further therapeutic tactics. At adequate selection of a dose of medicines the speed of psychophysical development reaches physiological norm, however lag in intelligence remains. Prevention consists in antenatalny protection of a fruit, medico-genetic consultation when planning pregnancy, a rational diet and the adequate use of iodine at incubation of the child.