pituitary disorder

2. Pituitary Disorders
 The pituitary gland, or the hypophysis, is a round structure about 1.27
cm (1⁄2 inch) in diameter located on the inferior aspect of the brain.
 It is divided into the anterior, intermediate, and posterior lobes.

3. The pituitary gland, the
relationship of the brain to
pituitary action, and the
hormones secreted by the
anterior pituitary and the
posterior pituitary.

4. PITUITARY FUNCTION AND DYSFUNCTION
 Commonly referred to as the master gland, the pituitary secretes
hormones that control the secretion of hormones by other endocrine
glands.
 The pituitary itself is controlled by the hypothalamus, an adjacent area
of the brain connected to the pituitary by the pituitary stalk.

5. Posterior Pituitary
 The important hormones secreted by the posterior lobe of the pituitary
gland are vasopressin (antidiuretic hormone [ADH]) and oxytocin.
 These hormones are synthesized in the hypothalamus and travel from
the hypothalamus to the posterior pituitary gland for storage.
 Vasopressin controls the excretion of water by the kidney; its secretion
is stimulated by an increase in the osmolality of the blood or by a
decrease in blood pressure.

6.  Oxytocin facilitates milk ejection during lactation and increases the
force of uterine contractions during labor and delivery.
 Oxytocin secretion is stimulated during pregnancy and at childbirth.

7. Anterior Pituitary
 The major hormones of the anterior pituitary gland are
folliclestimulating hormone (FSH), luteinizing hormone (LH),
prolactin, ACTH, thyroid-stimulating hormone (TSH), and growth
hormone (also referred to as somatotropin).
 The secretion of these major hormones is controlled by releasing
factors secreted by the hypothalamus.

8.  These releasing factors reach the anterior pituitary by way of the
bloodstream in a special circulation called the pituitary portal blood
system.
 Other hormones include melanocyte-stimulating hormone and beta-
lipotropin; the function of lipotropin is poorly understood.
 The hormones released by the anterior pituitary enter the general
circulation and are transported to their target organs.

9.  The main function of TSH, ACTH, FSH, and LH is the release of
hormones from other endocrine glands.
 Prolactin acts on the breast to stimulate milk production.
 Growth hormone has widespread effects on many target tissues.
 Growth hormone is a protein hormone that increases protein synthesis
in many tissues, increases the breakdown of fatty acids in adipose
tissue, and increases the glucose level in the blood.

10.  These actions of growth hormone are essential for normal growth,
although other hormones, such as thyroid hormone and insulin, are
required as well.
 Stress, exercise, and low blood glucose levels increase the secretion of
growth hormone.
 Abnormalities of pituitary function are caused by over secretion or
under secretion of any of the hormones produced or released by the
gland.
 Abnormalities of the anterior and posterior portions of the gland may
occur independently.

11.  Over secretion (hyper secretion) most commonly involves ACTH or
growth hormone and results in Cushing’s syndrome or acromegaly,
respectively.
 Acromegaly, an excess of growth hormone in adults, results in bone
and soft tissue deformities and enlargement of the viscera without an
increase in height.
 In children, over secretion of growth hormone results in gigantism,
with a person reaching 7 or even 8 feet tall.
 Conversely, insufficient secretion of growth hormone during
childhood results in generalized limited growth and dwarfism.

12.  Under secretion (hypo secretion) commonly involves all of the anterior
pituitary hormones and is termed panhypopituitarism.
 In this condition, the thyroid gland, the adrenal cortex, and the gonads
atrophy (shrink) because of loss of the trophic-stimulating hormones.
 The most common disorder related to posterior lobe dysfunction is
diabetes insipidus, a condition in which abnormally large volumes of
dilute urine are excreted as a result of deficient production of
vasopressin.

13. HYPOPITUITARISM
 Hypofunction of the pituitary gland (hypopituitarism) can result from
disease of the pituitary gland itself or of the hypothalamus, but the
result is essentially the same.
 Hypopituitarism may result from destruction of the anterior lobe of
the pituitary gland.
 Panhypopituitarism is total absence of all pituitary secretions and is
rare.

14.  Postpartum pituitary necrosis is another uncommon cause of failure of
the anterior pituitary.
 It is more likely to occur in women with severe blood loss,
hypovolemia, and hypotension at the time of delivery.

15.  Hypopituitarism is also a complication of radiation therapy to the
head and neck area.
 The total destruction of the pituitary gland by trauma, tumor, or
vascular lesion removes all stimuli that are normally received by the
thyroid, the gonads, and the adrenal glands.
 The result is extreme weight loss, emaciation, atrophy of all endocrine
glands and organs, hair loss, impotence, amenorrhea,
hypometabolism, and hypoglycemia.
 Coma and death occur if the missing hormones are not replaced.

16.  PITUITARY TUMORS
 Pituitary tumors are usually benign, although their location and effects
on hormone production by target organs can cause life threatening
effects.
 Three principal types of pituitary tumors represent an overgrowth of
 (1) eosinophilic cells,
 (2) basophilic cells, or
 (3) chromophobic cells (ie, cells with no affinity for either eosinophilic
or basophilic stains).

17. Clinical Manifestations
 Eosinophilic tumors that develop early in life result in gigantism.
 The affected person may be more than 7 feet tall and large in all
proportions, yet so weak and lethargic that he or she can hardly stand.
 If the disorder begins during adult life, the excessive skeletal growth
occurs only in the feet, the hands, the superciliary ridge, the molar
eminences, the nose, and the chin, giving rise to the clinical picture
called acromegaly.

18.  Enlargement, however, involves all tissues and organs of the body.
 Many of these patients suffer from severe headaches and visual
disturbances because the tumors exert pressure on the optic nerves.
 Assessment of central vision and visual fields may indicate loss of
color discrimination, diplopia (double vision), or blindness of a portion
of a field of vision.
 Decalcification of the skeleton, muscular weakness, and endocrine
disturbances, similar to those occurring in patients with
hyperthyroidism, also are associated with this type of tumor.

19.  Basophilic tumors give rise to Cushing’s syndrome with features
largely attributable to hyperadrenalism, including masculinization and
amenorrhea in females, truncal obesity, hypertension, osteoporosis,
and polycythemia.
 Chromophobic tumors represent 90% of pituitary tumors.
 These tumors usually produce no hormones but destroy the rest of the
pituitary gland, causing hypopituitarism.

20.  People with this disease are often obese and somnolent and exhibit
fine, scanty hair, dry, soft skin, a pasty complexion, and small bones.
 They also experience headaches, loss of libido, and visual defects
progressing to blindness.
 Other signs and symptoms include polyuria, polyphagia, a lowering of
the basal metabolic rate, and a subnormal body temperature.

21. Assessment and Diagnostic Findings
 Diagnostic evaluation requires a careful history and physical
examination, including assessment of visual acuity and visual fields.
 Computed tomography (CT) and magnetic resonance imaging (MRI)
are used to diagnose the presence and extent of pituitary tumors.
 Serum levels of pituitary hormones may be obtained along with
measurements of hormones of target organs (eg, thyroid, adrenal) to
assist in diagnosis if other information is inconclusive.

22. Medical Management
 Surgical removal of the pituitary tumor through a trans sphenoidal
approach is the usual treatment.
 Stereotactic radiation therapy, which requires use of a neurosurgery-
type stereotactic frame, may be used to deliver external-beam radiation
therapy precisely to the pituitary tumor with minimal effect on normal
tissue.
 Other treatments include conventional radiation therapy,
bromocriptine (dopamine antagonist), and octreotide (synthetic analog
of growth hormone).

23.  These medications inhibit the production or release of growth
hormone and may bring about marked improvement of symptoms.
 Octreotide (Sandostatin) may also be used preoperatively to improve
the patient’s clinical condition and to shrink the tumor.

24. SURGICAL MANAGEMENT: HYPOPHYSECTOMY
 Hypophysectomy, or removal of the pituitary gland, may be
performed to treat primary pituitary gland tumors.
 It is the treatment of choice in patients with Cushing’s syndrome due
to excessive production of ACTH by a tumor of the pituitary gland.
 Hypophysectomy may also be performed on occasion as a palliative
measure to relieve bone pain secondary to metastasis of malignant
lesions of the breast and prostate.

25.  Several approaches are used to remove or destroy the pituitary gland:
surgical removal by transfrontal, subcranial, or oronasal–
transsphenoidal approaches or irradiation or cryosurgery.
 Even if surgery succeeds at removing the tumor, many of the features
or symptoms of acromegaly will be unaffected .

26.  The absence of the pituitary gland alters the function of many body
systems.
 Menstruation ceases and infertility occurs after total or near-total
ablation of the pituitary gland.
 Replacement therapy with corticosteroids and thyroid hormone is
necessary; therefore, patient teaching is imperative.
 Thanking you.