Page 344 - Color Atlas Of Pathophysiology (S Silbernagl Et Al, Thieme 2000)

Lesions of the Hypothalamus
The hypothalamus integrates the body’s auto- Abnormal release of hypophyseal hormones
nomic, endocrine, and somatomotor functions. occurs with lesions in different parts of the hy-
Neurons in the hypothalamus are responsible pothalamus. As a result, the peripheral func-
for regulating various homeostatic functions tions regulated by the hormones are affected
such as food intake, electrolyte and water me- (→ A2). When ADH is not released diabetes in-
Systems tabolism, temperature regulation, and circa- sipidus develops in which the kidney can no
longer produce concentrated urine and may
dian rhythm. In addition, the functions are
excrete as much as 20 l of urine daily
adapted in the hypothalamus to the required
(→ p. 260).
behavioral patterns, such as the fight and
Neuromuscular and Sensory The programs required for the particular cause hyperfunction or hypofunction of the
flight reaction, nutritive or sexual behavior.
Abnormal release of gonadotropin can
peripheral hormonal glands. Increased release
behavioral patterns are stored in the hypothal-
of sex hormones can result in premature sex-
amus and are called up as needed, in particular
by the neurons of the limbic system.
ual maturation (precocious puberty), while re-
Circumscribed lesions in the hypothalamus
duced release brings about delayed sexual ma-
turity and infertility (→ p. 272ff.).
can occur as the result of tumors, trauma, or
inflammation, and they can produce profound
Longitudinal growth is promoted by the sex
thyrotropin-regulated thyroid hormones (→
A lesion in the anterior hypothalamus (in-
p. 280ff.). A reduced concentration of these
cluding the preoptic region) leads to distur-
10 disorders of autonomic regulation (→ A1). hormones, somatotropin (→ p. 262ff.), and the
bances of temperature regulation and circadian
hormones delays growth, reduced release of
rhythm (destruction of the suprachiasmal nu- the sex hormones retarding the fusion of the
cleus). It expresses itself, for example, in in- epiphyseal plates which may eventually cause
somnia. Also, as a result of lesions in the su- gigantism, despite the slower growth. Cortico-
praoptic and paraventricular nuclei, the anti- tropin inhibits longitudinal growth via the ac-
diuretic hormone (ADH) and oxytocin (see be- tion of cortisol.
low) are no longer formed, and there is no The main hormones that affect metabolism
sense of thirst. are somatotropin, thyroid hormones, and the
A lesion in the medial hypothalamus also adrenocortical hormones (→ p. 268ff.) which
results in disorders of temperature control are regulated by corticotropin. Abnormal re-
and the sense of thirst. At the same time there lease of the latter hormones can have massive
may be marked impairment of food intake. A metabolic effects. Thyroid and adrenocortical
lesion in the lateral part of the medial hypo- hormones also have a profound effect on the
thalamus stops the sensation of hunger. Such circulation. The adrenocortical hormones also
patients no longer have the urge to eat (apha- have an influence on the blood cells. They
gia), their food intake is inadequate, and they cause an increase in erythrocytes, thrombo-
lose weight (anorexia). Conversely, lesions of cytes and neutrophils, while decreasing the
the medial hypothalamus cause a craving for number of lymphocytes, plasma cells, and eo-
food (hyperphagia) and, because of the intake sinophils. They thus affect O 2 transport in
of hypercaloric food, lead to obesity. However, blood, blood clotting, and immune defenses
obesity or anorexia are only rarely due to a hy- (→ p. 268 ff.).
pothalamic lesion, but rather have psychologi-
cal causes (→ p. 26). Damage to the medial hy-
pothalamus also brings about disorders of
memory acquisition and emotions.
Lesions in the posterior hypothalamus lead
to poikilothermia, narcolepsy and memory gaps,
along with other complex autonomic and
334 emotional disorders.
Silbernagl/Lang, Color Atlas of Pathophysiology © 2000 Thieme
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