Causes of increased body temperature

The most common cause of increased body temperature is an infectious process of various etiologies, but a non-infectious inflammatory process is also possible (for example, during myocardial infarction or so-called autoimmune inflammation). Pyrogens formed during inflammation affect activated leukocytes, which synthesize interleukin-1 (as well as interleukin-6, tumor necrosis factor (TNF) and other biologically active substances), stimulating the formation of prostaglandin E2, under the influence of which the level of the "set point" of the thermoregulation center increases (and, accordingly, body temperature). Sometimes the causes of fever may remain unclear for a long time ("fever of unknown genesis syndrome").

Many malignant tumors are accompanied by an increase in body temperature, such as bronchogenic cancer or renal parenchyma tumor, but especially often lymphogranulomatosis, in which a prolonged high fever lasting many months is often observed. Fever in malignant tumors is included in the concept of "paraneoplastic syndrome".

An increase in body temperature can be caused by taking various medications, such as certain antibiotics and analgesics.

The endocrine system influences heat production. The most striking example is that increased thyroid function is often accompanied by a subfebrile body temperature.

An increase in body temperature is possible with lesions of the diencephalon of various etiologies (encephalitis, hemorrhage into the ventricles of the brain, etc.).

An increase in body temperature can also occur in so-called thermal diseases caused by a disturbance in the balance between the processes of heat production and heat transfer while maintaining the normal level of the "set point" of the hypothalamic thermoregulation center. In some cases, heat production or exogenous heat supply significantly exceeds the capabilities of the heat transfer mechanisms (at their maximum tension), in others, heat transfer processes are disrupted with normal heat production. A combination of both causes is possible. Body temperature increases despite the efforts of the thermoregulatory center to maintain it within normal limits.

In all cases, clarifying the cause of the increase in body temperature is of great importance. It should be emphasized once again that fever is not always infectious and, therefore, requires the appointment of antimicrobial treatment.

Temperature curve

Temperature curve - a graph of changes in body temperature over time. To record a temperature curve, a special temperature sheet is used, where the body temperature values (in degrees Celsius) are plotted along the abscissa axis, and the days with the details "morning" and "evening" are plotted along the ordinate axis. The body temperature is marked on the graph with dots, connecting which we get a temperature curve. The following types of temperature curves are distinguished.

• Constant fever (febris continua). Fluctuations in body temperature during the day do not exceed 1 °C, usually within 38-39 °C. This type of fever is typical for acute infectious diseases (pneumonia, acute respiratory viral infections (ARVI).
• Remittent or remittent fever (febris remittens). Body temperature increases to various values with daily fluctuations of 1-2 °C; characteristic of purulent diseases.
• Intermittent fever (febris intermittens). The body temperature suddenly rises to 39-40 °C and after some time (hours) quickly decreases to normal and even subnormal values. After 1-3 days, such a rise in temperature is repeated, etc. This type of fever is characteristic of malaria.
• Recurrent fever (febris recurrent). Unlike intermittent fever, the body temperature rises immediately to high values and remains at an elevated level for several days, then it temporarily drops to normal with a subsequent new period of increase (from 2 to 5 attacks). Recurrent fever is typical for some spirochitoses (relapsing fever).

• Hectic, or wasting, fever (febris hectica). Fluctuations in body temperature during the day are -3-5 °C. This type of temperature curve is especially characteristic of sepsis.
• Undulating fever (febris undulatts). The body temperature increases for some time from day to day, reaching higher and higher values, and then gradually, with each day, becomes lower and lower. Having reached subfebrile or normal levels, it again gives a fairly regular wave of rise, etc. A distinctive feature of undulating fever compared to recurrent fever is a gradual increase in body temperature and its equally gradual decline. Such fever in its most typical form is observed in brucellosis.
• Irregular fever (febris irregularis). It is characterized by irregular increases in body temperature to various values. Most often observed in rheumatism, flu, dysentery.
• Perverted fever (febris inversa). Morning body temperature is higher than evening. This type of temperature curve is sometimes observed in tuberculosis, protracted sepsis.

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