124. Pituitary gland disorders- acromegaly, Cushing's disease, pituitary cachexia, diabetes insipidus.

Question 1

What is the pituitary gland?

Answer 1

• a small, pea-sized endocrine gland located at the base of your brain below your hypothalamus
• It releases several important hormones and controls the function of many other endocrine system glands.

Question 2

Where is the pituitary gland found?

Answer 2

• is housed within a bony structure (sella turcica) at the base of the brain.
• The gland is attached to the hypothalamus (a part of the brain that affects the pituitary gland) by nerve fibers and blood vessels.

Question 3

What does the pituitary gland do?

Answer 3

to produce and release several hormones that help carry out important bodily functions

including:

Growth.

Metabolism (how your body transforms and manages the energy from the food you eat).

Reproduction.

Response to stress or trauma.

Lactation.

Water and sodium (salt)
balance.

Labor and childbirth.

Question 4

What is the general anatomy of the pituitary gland?

Answer 4

The pituitary gland lies at the middle of the base of the skull and is housed within a bony structure called the sella turcica, which is behind the nose and immediately beneath the hypothalamus.

The pituitary gland is attached to the hypothalamus by a stalk composed of neuronal axons and the so-called hypophyseal-portal veins.

• In most species the pituitary gland is divided into three lobes: the anterior lobe, the intermediate lobe, and the posterior lobe (also called the neurohypophysis or pars nervosa).
• In humans, the intermediate lobe does not exist as a distinct anatomic structure but rather remains only as cells dispersed within the anterior lobe.
• anterior pituitary contains abundant hormone-secreting epithelial cells, the posterior pituitary is composed largely of unmyelinated (lacking a sheath of fatty insulation) secretory neurons.

Question 5

What hormones are produced by the anterior pit. gland?

Answer 5

Adrenocorticotropic hormone (ACTH or corticotropin).

Follicle-stimulating hormone (FSH).

Growth hormone (GH).

Luteinizing hormone (LH).

Prolactin.

Thyroid-stimulating hormone (TSH).

Question 6

What hormones are produced by the post. pit. gland?

Answer 6

• Oxytocin

- Antidiuretic hormone (ADH, or vasopressin)

Question 7

What is the function of Prolactin?

Answer 7

Prolactin stimulates milk production.

Question 8

What is the function of TSH?

Answer 8

hyrotropin stimulates the production of thyroid hormone.

Question 9

What is the function of LH?

Answer 9

LH stimulates the production of estrogens and progesterone by the ovaries in women and the production of testosterone by the testes in men.

Question 10

What is the function of FSH?

Answer 10

FSH stimulates the production of estrogens and the growth of egg cells (oocytes) in the ovaries in women and sperm cells in the testes in men.

Question 11

What is the function of ACTH?

Answer 11

ACTH stimulates the production of cortisol and androgenic hormones by the adrenal cortex.

Question 12

What is the function of oxytocin?

Answer 12

Oxytocin stimulates contraction of the uterus, an important aspect of labour and parturition and of milk ejection during breast-feeding.

Question 13

What is the function of Vasopressin?

Answer 13

Vasopressin regulates blood pressure and increases reabsorption of water from the kidneys, thus conserving body water and defending against dehydration. Vasopressin secretion is stimulated by increased serum osmolality, which is an indication of dehydration.

Question 14

How are pituitary gland disorders classified?

Answer 14

• Hypopituitarism
• Hyperpituitarism
• Panhypopituitarism
• Pituitary tumours

Question 15

What is Hypopituitarism?

Answer 15

• a rare disorder in which your pituitary gland fails to produce one or more hormones, or doesn’t produce enough hormones.
• Hypopituitarism can develop suddenly after surgery, injury, or bleeding, or very slowly, over several months or even over several years.

Question 16

What are the different types of cells in the anterior pituitary gland?

Answer 16

• Thyrotrophs = synthesize thyrotropin (TSH)
• Gonadotrophs = LH, FSH
• Corticotrophs = adenocorticotropic hormone
• somatotrophs = GH
• lactrotrophs = prolactin

Question 17

What is hyperpituitarism?

Answer 17

• Having an overactive pituitary gland
• most commonly caused by noncancerous tumors.
• This causes the gland to secrete too much of certain kinds of hormones related to growth, reproduction, and metabolism, among other things.
• Cushing’s syndrome
• Acromegaly
• Prolactinoma
• Hyperthyroidism

Question 18

What is Acromegaly?

Answer 18

Acromegaly is a disorder that occurs when your body makes too much growth hormone (GH). Produced mainly in the pituitary gland, GH controls the physical growth of the body. In adults, too much of this hormone causes bones, cartilage, body organs, and other tissues to increase in size.

Question 19

What is acromegaly caused by?

Answer 19

This disorder is caused by secretion of excessive amounts of growth hormone (GH) in adults.

Question 20

What are the clinical features of acromegaly?

Answer 20

Acromegaly can cause:

Hands and feet to grow.

Change in facial structure — jaw and brow may stick out and the nose, tongue, and lips may get bigger.

Skin becoming thick, coarse, and oily.

Irregular periods in women and erectile dysfunction in men.

Increased risk for high blood pressure, diabetes, heart attack, and certain types of cancer.

In children and adolescents, excessive levels of growth hormone can result in a condition called gigantism. Children with this condition may have unusually long arms and legs and may grow to heights of 7 to 8 feet or more.

Question 21

What is Cushing’s disease?

hypercorticolism

Answer 21

A noncancerous (benign) tumor of the pituitary gland, located at the base of the brain, produces an excess amount of ACTH , which in turn stimulates the adrenal glands to make more cortisol. When this form of the syndrome develops, it’s called Cushing disease.

Question 22

What is the cause of Cushing’s disease?

Answer 22

If the pituitary gland secretes too much ACTH, the adrenal glands may release too much cortisol. Cortisol regulates the metabolism of proteins, fats, and carbohydrates. It is also involved in the body’s inflammatory and immune responses.

Question 23

What are the clinical features of Cushing’s disease?

Answer 23

Symptoms of Cushing’s disease may include:

Accumulation of fat in the upper body.

Excessive facial hair in women.

Pink or purplish stretch marks on the abdomen.

Tendency to bruise easily.

Bones may become fragile and tend to break more easily.

Question 24

What is pituitary cachexia?

Answer 24

Simmonds’ disease or pituitary cachexia is a syndrome ascribed to destruction or physiological exhaustion of the hypophysis (chiefly the anterior portion).

The destruction may be caused by embolic infarction, tumor, syphilis, tuberculosis, metastatic abscesses, inflammation, etc.

Clinically the Simmonds’ syndrome is characterized by:
cachexia,
premature senility,
atrophy of the gonads and genitalia,
with amenorrhea,
atrophy of the breasts,
loss of pubic and axillary hair, loss of libido,
integumental changes (chiefly dryness of the skin), anorexia and constipation, hypotension and muscular weakness, hypoglycemia, decreased sugar tolerance, lowered basal metabolism and depressed specific dynamic action of proteins, anemia, lymphocytosis and sometimes eosinophilia

Question 25

How is diabetes insipidus caused by pituitary dysfunction?

Answer 25

• Diabetes insipidus occurs when your body can’t properly balance the body’s fluid levels.
• The familial form of neurohypophyseal diabetes insipidus is caused by mutations in the AVP gene. This gene provides instructions for making a hormone called vasopressin or antidiuretic hormone (ADH). This hormone, which is produced and stored in the brain, helps control the body’s water balance.

AVP = arginine vasopressin

Question 26

What causes an overactive pituitary gland?

Answer 26

• Benign tumors are the most frequent cause of an overactive pituitary.
• Depending on which types of cells are affected, the pituitary gland will start to secrete excessive amounts of one or two hormones.
• In some cases, pituitary tumors may result from an inherited condition known as multiple endocrine neoplasia type 1(MEN1).
• This disorder also causes benign tumors of the pancreas and parathyroid glands.
• In rare cases, a cancerous tumor or a disorder of the hypothalamus may be the underlying cause.

Question 27

What are the acidophils?

Answer 27

• The pink acidophils secrete growth hormone (GH) and prolactin (PRL)

The adenohypophysis contains three major cell types: acidophils, basophils, and chromophobes.

The staining is variable, and to properly identify specific hormone secretion, immunohistochemical staining is necessary.

Question 28

What are the basophils?

Answer 28

• The dark purple basophils secrete corticotrophin (ACTH), thyroid stimulating hormone (TSH), and gonadotrophins follicle stimulating hormone-luteinizing hormone (FSH and LH)

The adenohypophysis contains three major cell types: acidophils, basophils, and chromophobes.

The staining is variable, and to properly identify specific hormone secretion, immunohistochemical staining is necessary.

Question 29

What are the chromophobes?

Answer 29

The pale staining chromophobes have few cytoplasmic granules, but may have secretory activity.

The adenohypophysis contains three major cell types: acidophils, basophils, and chromophobes.

The staining is variable, and to properly identify specific hormone secretion, immunohistochemical staining is necessary.

Question 30

What are the chromophobes?

Answer 30

The pale staining chromophobes have few cytoplasmic granules, but may have secretory activity.

The adenohypophysis contains three major cell types: acidophils, basophils, and chromophobes.

The staining is variable, and to properly identify specific hormone secretion, immunohistochemical staining is necessary.

Question 31

What is the histology of the posterior pituitary gland?

Answer 31

• resembles neural tissue
• glial cells, nerve endings, intra-axonal neurosecretory granules.
• The hormones vasopressin (antidiuretic hormone, or ADH) and oxytocin made in the hypothalamus (supraoptic and paraventricular nuclei) are transported into the intra-axonal neurosecretory granules where they are released.

Question 32

What is the histology of the posterior pituitary gland?

Answer 32

• resembles neural tissue
• glial cells, nerve endings, intra-axonal neurosecretory granules.
• The hormones vasopressin (antidiuretic hormone, or ADH) and oxytocin made in the hypothalamus (supraoptic and paraventricular nuclei) are transported into the intra-axonal neurosecretory granules where they are released.

Question 33

What are microadenomas of the pituitary gland?

Answer 33

• small benign tumours
• appear in 1-5% of adults
• Rarely have significant hormonal output that leads to clinical disease.
• They are not large enough to produce pressure effects on surrounding structures, so the sella turcica will not be enlarged, the optic chiasm will not be affected, and the remaining normal pituitary will continue to function.