Introduction

• Two functional components

1)     anterior lobe – adenohypophysis

Ø  derived from Rathke’s pouch

Ø  Secretory portion of the pituitary

Ø  Three morphological cell types (acidophils, basophils, chromophobes); Chromophobes make up the majority of the anterior lobe cells

Ø  Five functional cell types produce 6 hormones (PATFGL) – (Point after try, FGL = field goal)

1)     Prolactin – mammotrophs

2)     Adrenocorticotrophic hormone (ACTH) – corticotrophs

3)     Thyroid stimulating hormone (TSH) – thyrotrophs

4)     Follicle stimulating hormone (FSH) – gonadotrophs

5)     Growth Hormone – somatotrophs

6)     Leutinizing Hormone (LH) – somatotrophs

6 ½) Melanocyte stimulating hormone – corticotrophs

Ø  Corticotrophs produce proopiomelanocortin from which ACTH and MSH are produced

Ø  Mammotrophs and somatotrophs are acidophils

Ø  Corticotrophs, thyrotrophs, and gonadotrophs are basophils

2)     Posterior lobe – neurohypophysis

Ø  derived from outpouching of the 3^rd ventricle

Ø  contain unmyelinated nerve axons

Ø  neurohormones – vasopressin (ADH) and oxytocin

Pathological Processes involving the Pituitary Gland

• very few of them

1)     hypopituitarism

2)     hyperpituitarism

3)     posterior pituitary syndromes

4)     compression or invasion

Clinical Manifestations

Hyperpituitarism

• usually caused by 1^o pituitary tumor
• can also be caused by interruption of feedback inhibition from the hypothalamus
• Rare – primary hypothalamic origin

Hypopituitarism

• 75% obliteration of the anterior lobe (MAGIC # is 75%) KNOW FOR TEST!!!!
• Tumors, infections, etc.

Local Mass Effects

• sella turcica destruction or enlargement
• compression of the optic chiasm – bitemporal hemianopsia know for test!!!
• Increased ICP w/ or w/o hydrocephalus

Stalk Effect

• when tumor compresses the pituitary stalk it obstructs Dopamine’s inhibitory effect on Prolactin release

Pituitary Adenomas

Size (classified as Microadenomas and macroadenomas)

• Microadenomas – < 10 mm in max. diameter; may be incidental; found in 20% of autopsied patients
• Size does not determine likelihood of clinical manifestations

Location

• arise in the anterior lobe
• may invade posterior lobe or become extra-pituitary

Local effects

• Microadenomas – commonly compress the adjacent gland; may erode bone and extend into adjacent structures to become invasive
• Can extend along optic chiasm, cavernous sinus, cranial nerves, or sphenoid bone and sinuses

MICRO

• uniform growth of polygonal cells arranged in sheets, cords, nests, or papillae.
• Lack the regular, thick reticulin investment characteristic of adenohypophysis
• PITUITARY APOPLEXY – spontaneous hemorrhage 2^o to friable and richly vascular nature

Ø  results in sudden and dramatic clinical consequences

Ø  rapid enlargement allows no time for accomodation

Ø  headache is a typical complaint

Types

• Somatotrophic

Ø  5% are pure – produce GH exclusively

Ø  25% of pituitary adenomas produce GH alone or in combination with other hormones

Ø  Clinical

1)     acromegaly – enlargement of the hands, feet and head

2)     large tongue, broad nose, prominent jaw, soft tissue enlargement

3)     think Jay Leno

4)     Gigantism in children (because they haven’t had fusion of the bony epiphyses)

• Prolactinomas

Ø  MOST COMMON FORM OF PITUITARY ADENOMA (ON TEST!!!!)

Ø  Can be in children & cystic & form amyloid spheres

Ø  Rule out 2^o hyperprolactinemia – caused by drugs, hypothalamic lesions, Dopamine

Ø  2/3 are macro; 1/3 are micro

Ø  Clinical

1)     amenorrhea, infertility, impotence

2)     GALACTORRHEA

Ø  Treatment: bromocriptine (Dopamine agonist)

• Corticotrophic adenomas

Ø  usu micro and basophilic

Ø  Crooke’s hyaline may accumulate in the cytoplasm

Ø  Clinical

• looks like Cushing’s disease

1) “moon” facies, glucose intolerance, HTN, central/truncal obesity, abdominal skin striae, hirsuitism, hyperplastic adrenals bilaterally

Hypopituitarism

• results from lesions of the anterior lobe or the hypothalamus
• majority of cases (90%) result from destructive processes involveing the anterior lobe
• REMEMBER – 75% OBLITERATION to be non-functional or hypo-

Common Causes…

Nonsecretory pituitary Adenomas

• local effects only
• can be resected with removal of the pituitary

Sheehan’s Syndrome

• postpartum pituitary necrosis
• sudden infarction of the very vascular anterior lobe
• occurs 2^o to hypotension or obstetric hemorrhage
• During pregnancy – adenohypophysis enlarges to 2X its original size – compresses the vasculature
• During Hypotensive episode the vessels spasm and there is ischemic damage to the anterior lobe
• Other etiologies – DIC, Sickle Cell, Cavernous Sinus Thrombosis, diabetes mellitus, trauma, temporal arteritis
• Clinical Presentation

Ø  failure to lactate postpartum

Ø  gonadotrophic hormone deficiency

• leads to empty sella turcica syndrome

Empty Sella Syndrome

• most common – herniation of arachnoid through defect in diaphragma sella
• The increasing ICP leads to pressure atrophy of the pituitary gland
• Rare to significantly cause gland hypofunction

Iatrogenic:

Less commonly …

Tumors, metastases, craniopharyngiomas, gliomas, germ cell tumors, diabetes insipidus, growth acceleration, growth stunting, delayed puberty

Rarely …

2^o to arteritis, sarcoidosis, infections, metabolic disorders

Specific Deficiencies

• GH

Ø  adults – clinically cryptic

Ø  children – dwarfism, with growth and sexual retardation

• FSH and LH

Ø  amenorrhea, loss of axillary and pubic hair, sterility, ovarian and testicular atrophy

• TSH

Ø  hypothyroidism

Ø  rare

Hypothalamic Tumors

Craniopharyngiomas

• cystic and calcified, benign, slow growing
• suprasellar region
• children and young adults
• locally envasive – may compress optic chiasm, 3^rd ventricle, temporal lobes
• Pathology

Ø  derived from Rathke’s pouch

Ø  ameloblastic remnants

• GROSS

Ø  cystic, multioculated, calcified

• MICRO

Ø  cysts are lined by stratified squamous epithelium embedded in loos stroma

Ø  “wet keratin”

Gliomas

• Juvenile Pilocytic Astrocytoma, hamartomas

Posterior Pituitary Syndromes

• most result from suprasella tumors or iatrogenic disruption
• Two types of dysfunction

1)     vasopressin deficiency – leads to diabetes insipidus

2)     SIADH

• Diabetes insipidus

Ø  excessive thirst, polyuria, polydipsia

Ø  most commonly caused by ADH deficiency due to:

1)     neoplastic or inflammatory interruption of the hypothalamohypophyseal axis

2)     iatrogenic – surgery or radiation

3)     head injury

4)     idiopathic

5)     eosinophilic granuloma

• SIADH – syndrome of inappropriate ADH release

Ø  inappropriate release of ADH relative to the plasma osmolarity

Ø  Results in: 1) excessive resorption of H₂O by renal tubules, hyponatremia, HTN

Ø  Causes:

1)     paraneoplastic elaboration of ADH – most commonly small cell carcinoma

2)     pulmonary disorders – (pneumonia, TB)

3)     CNS abnormalities – intracranial hemorrhage, CNS infections

4)     Drugs

• Prolactin cell adenoma – highest frequency – 20-30%

Tags: acidophils, adenohypophysis, Adrenocorticotrophic hormone, Basophils, chromophobes, craniopharyngiomas, delayed puberty, diabetes insipidus, Empty Sella Syndrome, Follicle stimulating hormone, Germ Cell Tumors, gliomas, growth acceleration, Growth Hormone, growth stunting, hyperpituitarism, hypopituitarism, Leutinizing Hormone, mammotrophs, Metastases, neurohypophysis, Pituitary Adenomas, Prolactin, Prolactinomas, proopiomelanocortin, Rathke's pouch, Sheehan's Syndrome, Somatotrophic, Thyroid stimulating hormone, tumors

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