According to the general practitioner and cardiologist Ivan Likov, diseases of the thyroid gland are a common medical cause of increased fatigue.
In an interview with doctor Likov, a warning was sounded that increased fatigue may indicate hidden diseases. In particular, such a disease can be hypothyroidism, the manifestations of which are usually attributed to the consequences of overwork and lack of sleep.
Hypothyroidism means that the thyroid gland is weakened and can hardly cope with the task of producing hormones – their level decreases accordingly. Victims of this disease suffer from apathy, loss of tone, energy, but they explain this by many external circumstances
“In this condition, very often there is severe fatigue, weakness, lethargy, fatigue, weight gain, sometimes a pronounced edematous syndrome can be observed,” doctor Likov told Moscow 24.
For people experiencing increased fatigue, the doctor recommended examining the thyroid gland, take a blood test for hormones.
The specialist added that latent chronic viral infections can also provoke fatigue that interferes with leading a normal life.
“Very often, chronic fatigue syndrome is caused by the Epstein-Barr virus,” Ivan Likov informed.
He called anemia, in which the content of red blood cells and oxygen decreases, and immunity weakens, another hidden cause of fatigue. Anemia is provoked by a lack of iron, as well as vitamin B12.
The doctor named the reasons for the regular increase in heart rate
In addition, depression, characterized by impaired production of neurotransmitter substances in the brain, leads to a state of constant fatigue and lethargy. providing the psyche with the opportunity to relax and experience pleasant emotions.
A change in the color of plaque on the tongue can indicate diseases
Earlier, the MedikForum.ru portal wrote that recently people have been increasingly diagnosed with this type stress as moral burnout. 
Ivan Likov Health doctor -therapist, cardiologist of the Central Clinical Hospital of the Administration of the President of the Russian Federation