Page 730 - Robbins Basic Pathology by Vinay Kumar, Abul K. Abbas, Jon C. Aster
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716 C H A P T E R 19 Endocrine System overproduction of hormones, with associated biochemical
and clinical consequences, or (2) diseases associated with
thereby affecting the expression of specific target genes. the development of mass lesions, which may be nonfunc-
Hormones of this type include the steroids (e.g., estrogen, tional or may be associated with overproduction or under-
progesterone, glucocorticoids), the retinoids (vitamin A), production of hormones.
and thyroxine.
Several processes may disturb the normal activity of the With the exception of mass lesions, study of endocrine
endocrine system, including impaired synthesis or release diseases relies heavily on biochemical measurements of
of hormones, abnormal interactions between hormones the levels of hormones, their regulators, and other
and their target tissues, and abnormal responses of target metabolites.
organs to their hormones. Endocrine diseases can be
generally classified as (1) diseases of underproduction or
PITUITARY in turn under the control of factors produced in the hypo-
thalamus; while most hypothalamic factors are stimulatory
The pituitary gland is a small, bean-shaped structure that and promote pituitary hormone release, others (e.g., soma-
lies at the base of the brain within the confines of the sella tostatin and dopamine) are inhibitory in their effects (Fig.
turcica. It is intimately related to the hypothalamus, with 19–2). Rarely, signs and symptoms of pituitary disease may
which it is connected by both a stalk, composed of axons be caused by excess or lack of the hypothalamic factors,
extending from the hypothalamus, and a rich venous rather than by a primary pituitary abnormality.
plexus constituting a portal circulation. Along with the
hypothalamus, the pituitary has a central role in the regula- Symptoms and signs of pituitary disease can be grouped
tion of most of the other endocrine glands. The pituitary is as follows:
composed of two morphologically and functionally dis-
tinct components: the anterior lobe (adenohypophysis) and • Hyperpituitarism-related effects: Hyperpituitarism arises
the posterior lobe (neurohypophysis). Diseases of the pitu- from excessive secretion of trophic hormones. It most
itary, accordingly, can be divided into those that primarily often results from an anterior pituitary adenoma but also
affect the anterior lobe and those that primarily affect the may be caused by other pituitary and extrapituitary
posterior lobe. lesions, as described subsequently. The symptoms and
signs of hyperpituitarism are discussed in the context of
The anterior pituitary, or adenohypophysis, is composed of individual tumors, later in the chapter.
epithelial cells derived embryologically from the develop-
ing oral cavity. In routine histologic sections, a colorful • Hypopituitarism-related effects: Hypopituitarism is
array of cells containing basophilic cytoplasm, eosinophilic caused by deficiency of trophic hormones and results
cytoplasm, or poorly staining (chromophobic) cytoplasm is from a variety of destructive processes, including isch-
present (Fig. 19–1). Detailed studies using electron micros emic injury, surgery or radiation, and inflammatory reac-
copy and immunocytochemical techniques have demon- tions. In addition, nonfunctional pituitary adenomas may
strated that the staining properties of these cells are related encroach upon and destroy adjacent normal anterior
to the presence of various trophic polypeptide hormones pituitary parenchyma, causing hypopituitarism.
within their cytoplasm. The release of trophic hormones is
• Local mass effects: Among the earliest changes referable
Figure 19–1 Normal architecture of the anterior pituitary. The gland to mass effect are radiographic abnormalities of the sella
is populated by several distinct cell types containing a variety of stimulat- turcica, including sellar expansion, bony erosion, and
ing (trophic) hormones. Each of the hormones has different staining disruption of the diaphragma sellae. Because of the close
characteristics, resulting in a mixture of cell types in routine histologic proximity of the optic nerves and chiasm to the sella,
preparations. Note also the presence of a fine reticulin network. expanding pituitary lesions often compress decussating
fibers in the optic chiasm. This altered neuroanatomy
gives rise to visual field abnormalities, classically in the
form of defects in the lateral (temporal) visual fields—a
so-called bitemporal hemianopsia. As in the case of any
expanding intracranial mass, pituitary adenomas may
produce signs and symptoms of elevated intracranial pres-
sure, including headache, nausea, and vomiting. Pitu-
itary adenomas that extend beyond the sella turcica into
the base of the brain (invasive pituitary adenoma)
produce seizures or obstructive hydrocephalus; involve-
ment of cranial nerves can result in cranial nerve palsy.
On occasion, acute hemorrhage into an adenoma is asso-
ciated with clinical evidence of rapid enlargement of the
lesion and depression of consciousness, a situation
appropriately termed pituitary apoplexy. Acute pituitary
apoplexy constitutes a neurosurgical emergency,
because it may be rapidly fatal.
