Endocrinology- Hypopituitarsm and posterior pituitary syndromes

Question 1

refers to decreased secretion of pituitary hormones, which can result from diseases of the hypothalamus or of the pituitary.

Answer 1

Hypopituitarism

Question 2

Hypofunction of the anterior pituitary occurs
when approximately_______________

This may be congenital or the
result of a variety of acquired abnormalities that are intrinsic to the pituitary.

Answer 2

75% of the parenchyma is lost or absent.

Question 3

Hypopituitarism
accompanied by evidence of posterior pituitary dysfunction in the form of diabetes insipidus
(see below) is almost always of ______________-.

Most cases of hypofunction arise from
destructive processes directly involving the anterior pituitary, although other mechanisms have
been identified.

Answer 3

hypothalamic origin

Question 4

Pituitary adenomas, other benign tumors arising within
the sella, primary and metastatic malignancies, and cysts can cause hypopituitarism.
Any mass lesion in the sella can cause damage by exerting pressure on adjacent
pituitary cells.

Answer 4

Tumors and other mass lesions:

Question 5

___________________ are among the most common
causes of pituitary hypofunction

Answer 5

Traumatic brain injury and subarachnoid hemorrhage

Question 6

: Surgical excision of a pituitary adenoma may inadvertently
extend to the nonadenomatous pituitary.

Radiation of the pituitary, used to prevent
regrowth of residual tumor after surgery, can damage the nonadenomatous pituitary.

Answer 6

Pituitary surgery or radiation

Question 7

As has been mentioned, this is a sudden hemorrhage into the
pituitary gland, often occurring into a pituitary adenoma.

Answer 7

Pituitary apoplexy:

Question 8

What is the presentation of pituitary apoplexy?

Answer 8

In its most dramatic
presentation, apoplexy causes the sudden onset of excruciating headache, diplopia due
to pressure on the oculomotor nerves, and hypopituitarism.

In severe cases, it can
cause cardiovascular collapse, loss of consciousness, and even sudden death.

Thus,
pituitary apoplexy is a neurosurgical emergency.

Question 9

______________-of the anterior pituitary, is the most common form of clinically significant ischemic necrosis of the anterior pituitary.

Answer 9

: Sheehan syndrome , or postpartum necrosis

Question 10

WHat is the pathophysiology of sheehans syndrome?

Answer 10

• During pregnancy the anterior pituitary enlarges to almost twice its normal size.
• This physiologic expansion of the gland is not accompanied by an increase in blood supply from the low-pressure venous system; hence, there is relative anoxia.
• Further reduction in blood supply caused by obstetric hemorrhage or shock may precipitate infarction of the anterior lobe.
• The posterior pituitary, because it receives its blood directly from arterial branches, is much less susceptible to ischemic injury and is therefore usually not affected.
  *

Question 11

Pituitary necrosis can also be encountered in such cases:

Answer 11

​Pituitary necrosis may also be encountered in other conditions, such as:

• disseminated intravascular coagulation and
• (more rarely) sickle cell anemia,
• elevated intracranial pressure,
• traumatic injury,
• and shock of any origin.

Whatever the pathogenesis, the ischemic area is resorbed and replaced by a nubbin of fibrous tissue attached to the wall of an empty sella.

Question 12

These cysts, lined by ciliated cuboidal epithelium with occasional
goblet cellsandanterior pituitary cells, canaccumulate proteinaceous fluid and expand,
compromising the normal gland

Answer 12

Rathke cleft cyst:

Question 13

Any condition that destroys part or all of the pituitary gland, such
as ablation of the pituitary by surgery or radiation, can result in an empty sella.

These syndrome refers to the presence of an enlarged, empty sella turcica.

Answer 13

Empty sella syndrome:

Question 14

There are two types of emty sellar syndrome:

Answer 14

There
are two types:

(1) In a primary empty sella

(2) In a
secondary empty sella

Question 16

In a____________there is a defect in the diaphragma sella that

• *allows the arachnoid mater** and cerebrospinal fluid to herniate into the sella, resulting in
• *expansion of the sella and compression of the pituitary**.

Answer 16

primary empty sella,

Question 17

Who are classically affected in primary emty sella?

Answer 17

Classically, affected patients are

obese women with a history of multiple pregnancies.

Question 18

The empty sella syndrome may be

associated with

Answer 18

• visual field defects and
• occasionally with endocrine anomalies,
• such as hyperprolactinemia, as a result of interruption of inhibitory hypothalamic effects.
• Loss of functioning parenchyma can be severe enough to result in hypopituitarism

Question 19

(2) In a
_____________, a mass, such as a pituitary adenoma, enlarges the sella, but then it is either surgically removed or undergoes spontaneous necrosis, leading to loss
of pituitary function.

Hypopituitarism can result from the treatment or spontaneous
infarction.

Answer 19

secondary empty sella

Question 20

Genetic defects:

Congenital deficiency of transcription factors required for normal
pituitary function is a rare cause of hypopituitarism.

For example, mutation of the
___________________) results in
combined pituitary hormone deficiency, characterized by deficiencies of GH, prolactin,
and TSH.

Answer 20

pituitary-specific homeobox gene POU1F1 (previously known as PIT-1

Question 21

Hypothalamic lesions:

As mentioned above, hypothalamic lesions can also affect the
pituitary by interfering with the delivery of pituitary hormone–releasing factors.

In
contrast to diseases that involve the pituitary directly, hypothalamic abnormalities can
also diminish the secretion of ADH, resulting in diabetes insipidus (discussed later).
Hypothalamic lesions that cause hypopituitarism include tumors, including benign
lesions that arise in the region of the hypothalamus, such as craniopharyngiomas, and
malignant tumors that metastasize to this site, such as breast and lung carcinomas.
Hypothalamic hormone deficiency can ensue when brain or nasopharyngeal tumors are
treated with radiation.

Question 22

Inflammatory disorders and infections , such as _____________________
can cause deficiencies of anterior pituitary hormones and diabetes insipidus.

Answer 22

sarcoidosis or tuberculous meningitis,

Question 23

The clinical manifestations of anterior pituitary hypofunction can be \_\_\_\_\_\_\_\_\_\_\_\_-, and depend on the
specific hormone(s) that are lacking.

Children can develop growth failure (pituitary dwarfism)
due to growth hormone deficiency.

Gonadotropin (LH and FSH) deficiency leads to amenorrhea
and infertility in women and decreased libido, impotence, and loss of pubic and axillary hair in
men

. TSH and ACTH deficiencies result in symptoms of hypothyroidism and hypoadrenalism,
respectively, and are discussed later in the chapter.

Prolactin deficiency results in failure of
postpartum lactation.

The anterior pituitary is also a rich source of MSH, synthesized from the
same precursor molecule that produces ACTH; therefore, one of the manifestations of
hypopituitarism includes pallor due to a loss of stimulatory effects of MSH on melanocytes.

Answer 23

protean

Question 24

Posterior Pituitary Syndromes
The clinically relevant posterior pituitary syndromes involve

Answer 24

• ADH and include diabetes insipidus
• and secretion of inappropriately high levels of ADH .

Question 25

________________ deficiency causes diabetes insipidus, a condition characterized

by excessive urination (polyuria) due to an inability of the kidney to resorb water
properly from the urine

. It can result from a variety of processes, including head trauma,
tumors, and inflammatory disorders of the hypothalamus and pituitary as well as surgical
procedures involving these organs.

The condition can also arise spontaneously, in the
absence of an underlying disorder.

Answer 25

ADH

Question 26

Diabetes insipidus from ADH deficiency is
designated as _____________ to differentiate it from nephrogenic diabetes insipidus, which is a
result of renal tubular unresponsiveness to circulating ADH.

Answer 26

central

Question 27

The clinical manifestation of central diabetes insipidus and peripheral are:

Answer 27

The clinical manifestations
of the two diseases are similar and include the

• excretion of large volumes of dilute urine
• with an inappropriately low specific gravity.
• Serum sodium and osmolality are increased
• as a result of excessive renal loss of free water, resulting in thirst and polydipsia.
• Patients who can drink water can generally compensate for urinary losses;
• patients who
• are obtunded, bedridden, or otherwise limited in their ability to obtain water may develop
• life-threatening dehydration.

Question 28

. ADH excess causes resorption of
excessive amounts of free water, resulting in hyponatremia.

Answer 28

Syndrome of inappropriate ADH (SIADH) secretion

Question 29

. ADH excess causes resorption of excessive amounts of free water, resulting in hyponatremia.

Answer 29

Syndrome of inappropriate ADH (SIADH) secretion

Question 30

The most frequent causes of SIADH include the ________________. [6]

Answer 30

• secretion of ectopic ADH by malignant neoplasms (particularly small-cell carcinomas of the lung),
• drugs that increase ADH secretion,
• and a variety of central nervous system disorders, including infections and trauma

Question 31

What are the clinical manifestation of SIADH?

Answer 31

The clinical manifestations of SIADH are dominated by hyponatremia, cerebral edema, and resultant neurologic dysfunction. Although total body water is increased, blood volume remains normal, and peripheral edema does not develop.