patho sheet # 12 - Yusr Al-takreety

Pathology
Lec.12
Week 5
07\02\2011
Dr. kramella

ENDOCRINE SYSTEM: The pituitary gland

Anatomy:
The pituitary gland is anatomically found in the sella turcica of the skull and it is connected to the hypothalamus by the stock. It is divided into two lobes the anterior lobe (adenohypophysis that accounts for 80% of the gland) and the posterior one (neurohypophysis that accounts for the rest).

Blood supply:
From portal circulation.

Secretions:
The pituitary hormones are secreted through the hypothalamus and controlled by the tropic hormones that are secreted by the hypothalamus.

TRH stimulate the secretion of TSH.
PIF (dopamine) inhibits the secretion of prolactin in thyroid for the breast.
CRH stimulates the secretion of ACTH that controls adrenal gland.
GNRH stimulates the secretion of GH.
SOMATOSTATIN inhibits the secretion of GH.
GNRH stimulates the secretion of both LH and FSH that controls the ovary and testicles.
THYROTROPHS secrets TSH.
*** notice that all hormones are stimulatory except dopamine and somatostatin are inhibitory.

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The anterior lobe (adenohypophysis):■
Contains 3 types of cells: the acidophiles, the basophiles and the chromo phobic cells.
Somatotrophs that secrete growth hormones and lactotrophs that secrete prolactin are acidophilic while corticotrophs that secrete ACTH, MSH are basophiles.
NOTICE that corticotrophs secrete both ACTH AND MSH (they have the same precursor molecule. so every time ACTH is secreted, MSH is secreted too (melanocyte secreting hormone that leads to skin pigmentation).

Hyperpituitarism:
In many instances it is caused by adenoma in the anterior pituitary lobe. They are responsible for 10% of the intracranial neoplasm, 3% of cases associated with multiple endocrine neoplasia type 1.
If the size of adenoma is less than 1 CM in diameter, they are called micro adenoma, and if it is more than 1 CM then it is called macro adenoma.
NON functional adenoma (they don't secrete hormones) are more likely to be macro adenoma because if the adenoma is secreting hormones that means these hormones will cause signs and symptoms to the patient and allow as to diagnose the adenoma early with its small size (micro adenoma) but if it does not secrete hormone then it will increase in size until it causes local effects like on bone or sella turcica (diagnosed radio logically or due to increase pressure on sella turcica because of its large size).
Pituitary apoplexy
Rapidly enlarging mass due to acute hemorrhage in an adenoma. It is an immuno-sergical emergency because it increases the intracranial pressure quickly (life threatening that’s why we have to discover it early).

Endocrine abnormalities:
-mass effect to due the presence of adenoma in the sella turcica, this will lead to radiographic abnormalities in the x-ray.
-visual field abnormalities: presence of adenoma will first affect the decussating fibers of the optic nerve (the anterior and lateral fibers that are responsible for the lateral temporal visual field) located directly above the sella turcica.the resulting is hemeanopsia,this in turn may lead to increase intracranial pressure or hypopituitarism(because when adenoma get enlarged it will press the residual normal pituitary tissues and may cause necrosis so the gland will not secrete its necessary hormones any more).

Adenomas of pituitary:
1. Prolactinomas
-most common type of pituitary adenomas.
-most frequent type of hyper functioning pituitary adenoma.
-they are responsible for 30% of all clinically recognized adenomas.
-they are weakly acidophilic or chromo phobic cells.
-they secrete sufficient prolactin to cause hyper prolactinemia and the serum prolactin level correlates with the adenoma size.
-signs and symptoms in females cause ammenourea, galactorea, loss of libido and infertility. it is more common in women 20 to 40 years of age.

Other causes of hyper prolactinemia:
-pregnancy
-nipple stimulation
-stress
-stalk effect due to head trauma or supra sellar mass.(in another word, we all know that the inhibitory effect of dopamine reaches the pituitary gland through the stalk from the hypothalamus.so anything affects that stalk intracranially(head trauma) may cause decrease in the effect of dopamine and so causes hyperprolactinemia.
-drugs
-estrogen
-hypothyroidism
-renal failure

Treatement: dopamine receptor agonists (bromo creptine that decreases prolactin level and size of adenoma).

2. Growth hormone amenoma:
-Second most common type.
-there is persistent secretion of growth hormone that increases the hepatic secretion of insulin like growth factor 1.
-causes gigantism (increase length of the long bones in hands and feet) before closure of the epiphysis, while acromegally (increase in the size of the organs) caused after the closure of the epiphysis.
-hyper osteosis: increase thickness of bones.
Protrusion of the jaw
Enlargement of the hands and feet.
Gonadal dysfunction.
Diabetes mellitus.
Muscle weakness.
Hypertension.
Congestive heart failure.
Increase risk of gastrointestinal cancers.
Increase prolactin.the cause is that some times the same cells that secrete growth hormone, secrete prolactin as well.

Treatment: surgical removal or radiation therapy. Overgrowth related symptoms relieve gradually and metabolic abnormalities improve with treatment.

3. Corticotroph cell adenoma:
-micro adenoma.
-they cause increase in ACTH due to minor pituitary tumors (major cause) followed by increase in cortisol and this causes cushion disease.
***anything causes increase in corticosteroids leads to what we call it cushion disease (cortisol tablets for treatment of inflammatory and autoimmune disorders, tumor in adrenal secreting cortisol).
Cushion disease is the most common endogenous cause of cushion syndrome.

4. Nelson syndrome:
-loss of inhibitory effect of corticosteroids results in massive hyper pigmentation but not hyper ….
***in the past cushion syndrome was treated by surgical removal of both adrenals (excision) so the ACTH will rise (no –ve feed back) and therefore MSH will rise too leading to hyper pigmentation to the skin. NO cortisol because there is NO adrenals.
-they are non-functioning cell adenomas.

5. Gonadotroph adenoma:
-responsible for 10-15% of pituitary adenomas.
-recently they discovered that what they used to call non-functioning or non-cell adenomas are in fact gonadotroph adenomas (they have LH or FSH)
-difficult to recognize insufficient and variable hormone production.

6. Thyrotroph?? Adenomas:
-they are responsible for 1% of pituitary adenomas.
-rare cause of hyper thyroidism.
-they don't cause any signs and symptoms until they form a large mass in the sella turcica or press the normal residual pituitary tissues and cause hypopituitarism.

7. Pituitary carcinomas:
-very rare.
-diagnosis requires demonstration of metastasis usually to lymph node, bone or liver (means, if we find vascular changes, pleomorphism,fibrosis or local invasion these are NOT carcinomas because we must see a metastasis to call them so).

*** Endocrine Atypia: conditions in the pituitary gland in which we find many features of carcinoma but we don't call them malignant tumors unless we see a metastasis (very important).

Hypopituitarism:
Decrease secretion of pituitary hormones. it occurs when more than 75% of the parenchyma is lost or absent which means we need only 25% of the anterior pituitary hormones during our whole life.
Causes are tumors, radiations, surgery or … cleft (embyrologically it arises from the oral cavity and it gives the origin of the pituitary gland).

Ischemic necrosis:
Like anti sella turcica, Sheehan syndrome, genetic defects, hypothalamic lesions, tumors like "craniopharyngioma" and infiltrative disorders "like tuberculosis and sarcoidosis" especially in the hypothalamus.

Sheehan syndrome:
Postpartum hypopituitarism due to postpartum hemorrhage. During pregnancy the pituitary gland develops hypertrophy and hyperplasia without increase in the blood supply to that gland. So in case the hemorrhage occurs after birth, it will affect the gland and causes infarction leading to hypopituitarism (COMPLETE loss of hormones) followed by hypothyroidism, hypoadrenalism and hypoganadism.

Anti sella turcica syndrome:
Results from hernia in the meninges containing CSF in the sella turcica, it presses the pituitary tissues and causes hypopituitarism.it usually occurs in multi pars obese ladies.

Craniopharyngiomas:
Tumors in the hypothalamus.

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■The posterior lobe (neuropophysis):
Contains the ADH and OXYTOCIN hormones.ADH function is absorption of water from the collecting tubules while oxytocin functioning on the myoepithilial cells of the breast to express milk.
There are NO clinical syndromes associated with oxytocin deficiency but they are exist with excess or deficiency in ADH.

Diabetes insipidus:
Deficiency in ADH resulting in poly urea, increase sodium osmolarity, thirst and poly pepsia.
If the patient is obtunded bedridden life-threatening dehydration will result.

Syndrome of inappropriate ADH secretion:
Secretion of ADH by neuroendocrine tumors most importantly and common cause is the small cell carcinomas of the lung (they secrete ADH and ACTH).
Increase ADH secretion causes hypo natremia (decrease sodium concentration in the blood), cerebral edema and neurological dysfunction that could end up with seizures.
Total body water increases while blood volume remains normal and peripheral edema doesn't occur.
***notice these people will develop intra cellular (not in the interstitium) cerebral edema not peripheral and the reason is that the brain is confined within the skull.

Hypothalamic sella turcical tumors:
Gliomas of the optic chiasm and craniopharyngiomas (derived from the stitial remnant oh the rashskes botch" embryologic origin of the anterior pituitary".
They are mostly supra sellar responsible for 1-5 % of intracranial tumors. They occur most commonly in childhood and adolescence causing growth retardation in children, visual disturbances in adults and pituitary hormonal deficiencies.
They are more commonly cystic sometimes multi loculated.they can cause sufficient calcification to be recognized radio graphically.
Histologically: two forms adementomenatous and papillary. Papillary lacks the wet keratin, calcification and cystic contents that are seen in the adementomenatous.


GOOD LUCK


Done by: Yusur AL-Tikriti.