When hypothyroidism develops atrophy and edema of the mucous membrane of the stomach and intestines, as well as reduced motor function of the gastrointestinal tract. Clinically, this is manifested by chronic gastritis (loss of appetite, a feeling of heaviness in the epigastrium after eating, burping with air, decrease in acidity and volume of gastric juice), impaired absorption of the intestine. Violation of the motor function of the gastrointestinal tract leads to nausea, vomiting, stretching of the stomach, intestines, severe constipation, in severe cases – to megacolon, and even paralytic intestinal obstruction.
Renal function in hypothyroidism is impaired. The rate of renal blood flow, glomerular filtration decreases, which leads to a decrease in diuresis, fluid retention and sodium in the body. In urine tests, proteinuria is noted. Patients are predisposed to the development of chronic pyelonephritis.
Due to the swelling of the nasal mucosa, nasal breathing is difficult. Vasomotor rhinitis is often observed. Patients are predisposed to the development of pneumonia and acute respiratory viral diseases.
In 80% of patients there is a lesion of the peripheral nervous system in the form of mononeuropathy. This is manifested by paresthesias, numbness of the arms, legs, development of carpal, cubital tunnel syndromes is possible (due to compression of the nerve trunks in the bone-ligamentous channels), a decrease in tendon reflexes is characteristic.
The violation of the functional state of the brain is manifested by a decrease in memory, mental performance, uncriticality towards oneself, others, noncommunity, lethargy, drowsiness. In severe cases, mental disorders are possible: depression, hallucinations, delusions.
Since thyroid hormones are necessary for maturation and differentiation of the central nervous system, in case of congenital hypothyroidism in the absence of timely replacement therapy with thyroid hormones, normal mental development is disturbed, mental underdevelopment (cretinism) is observed.