1. Diseases of pituitary gland
Ali Al Khader, M.D.
Faculty of Medicine
Al-Balqa’ Applied University

2. A brief introduction Anterior lobe = adenohypophysis
Posterior lobe = neurohypophysis
The production of most pituitary hormones is controlled in large part by positively and negatively acting factors from the hypothalamus (we are talking about the hormones of the anterior lobe)
Normal histology of anterior pituitary: 3 types of cells according to cytoplasmic staining:
acidophils-basophils-chromophobes

3. Introduction, 6 terminally differentiated cell types in the anterior pituitary

4. Introduction, the posterior pituitary
Pituicytes (modified glial cells) + axon terminals (from the axons that extend from the hypothalamus through the pituitary stalk)
Oxytocin & vasopressin (ADH)
…peptide hormones
…synthesized in the hypothalamus and stored in the axon terminals

5. Clinical manifestations of pituitary disease (3 categories)
Hyperpituitarism:
Due to:
-anterior pituitary hyperplasia, adenoma or carcinoma
-secretion from nonpituitary tumors
-certain hypothalamic disorders
Hypopituitarism:
-destruction of anterior pituitary (ischemia, surgery, radiation, inflammation)
-nonfunctional pituitary adenomas
Local mass effects:
…Due to a large pituitary tumor
…this can be seen as radiographic abnormality of sella turcica (sellar expansion, bony erosion or diaphragm sella disruption)
…bitemporal hemianopsia…due to the compression on optic chiasm…also some nonspecific visual abnormalities
…elevated intracranial pressure (headache & vomiting)
…in certain cases, sudden hemorrhage in an adenoma may cause sudden enlargement (= pituitary apoplexy)…emergency
…occasionally as: hypopituitarism
We are mainly talking here about the anterior pituitary
…the posterior pituitary diseases usually manifest as decreased or increased ADH

6. Pituitary adenomas
The most common cause of hyperpituitarism is: pituitary adenoma
Usually adults (35-60 years)
Microadenomas (<1cm) and macroadenomas if larger
Non-functional adenomas are likely to come to clinical attention at a later stage than those associated with endocrine abnormalities and are therefore more likely to be macroadenomas
In 14% of autopsies…the vast majority are clinically silent microadenomas (incidentalomas)

7. Pituitary adenomas, classification
This classification is according to immunohistochemical staining (not overproduction in the blood)

8. Pituitary adenomas, additional notes
Some pituitary adenomas can secrete two hormones (GH and prolactin being the most common combination), and rarely, pituitary adenomas are plurihormonal
Pituitary adenomas can be functional (i.e., associated with hormone excess and clinical manifestations) or nonfunctioning (i.e., without clinical symptoms of hormone excess)
Large pituitary adenomas, and particularly nonfunctioning ones, may cause hypopituitarism by encroaching on and destroying the adjacent anterior pituitary parenchyma

9. Pituitary adenomas, molecular pathology
rare

10. GNAS mutation (common in pituitary, thyroid & parathyroid adenomas)
In 40% of somatotroph adenomas and minority of corticotroph ones
…not thyrotroph, lactotroph or gonadotroph ones

11. Pituitary adenomas, morphology
Soft and well-circumscribed
…however,
in 30% of cases, they infiltrate neighboring tissues and on occasion, the brain itself…these are called: invasive adenomas (not cancer)
Macroadenomas are more to be invasive and more to have necrosis/hemorrhage
Histologically: uniform/monomorphic, polygonal cells arrayed in sheets or cords…less reticulin (supporting connective tissue) network (so: soft and gelatinous)
*Mitoses are rare
*The cells may be acidophilic,
basophilic or chromophobic…but usually monomorphic
Important differences from hyperplasia
“Atypical adenoma”: TP53 mutation, more mitoses, more
invasion & more recurrence

12. Lactotroph adenoma
The most frequent type of hyperfunctioning pituitary adenoma, accounting for about 30% of all clinically recognized cases
The prolactinemia will cause: amenorrhea, galactorrhea, loss of libido, and infertility
Prolactin secretion by functioning adenomas is usually efficient (even microadenomas secrete sufficient prolactin to cause hyperprolactinemia)
Diagnosis is easier in women (20-40 years) because of menstrual changes
Lactotroph adenoma underlies almost a quarter of cases of amenorrhea
In men and older women, the hormonal manifestations may be subtle, allowing the tumors to reach considerable size (macroadenomas) before being detected clinically
Remember that prolactin levels can be also elevated by nipple stimulation, as occurs during suckling in lactating women, and as a response to many types of stress

13. Some other pathologic causes of hyperprolactinemia
Morphology of lactotroph adenoma
*Sparsely granulated or densely granulated according to EM features of the cells
*Lactotroph adenomas have a propensity to undergo dystrophic calcification, ranging from isolated psammoma bodies to extensive calcification of virtually the entire tumor mass (“pituitary stone”)
Loss of dopamine-mediated inhibition of prolactin secretion
-damage of the dopaminergic neurons of the hypothalamus
-damage of the pituitary stalk (e.g., due to head trauma)
-exposure to drugs that block dopamine receptors on lactotroph cells
-any mass in the suprasellar compartment (e.g., a pituitary adenoma) may disturb the normal inhibitory influence of the hypothalamus on prolactin secretion…so: a non-prolactin-producing pituitary adenoma may cause mild prolactinemia if large enough
Renal failure
Hypothyroidism
Treatment of lactotroph adenomas
Surgery or, more commonly, with bromocriptine, a dopamine receptor agonist that causes the lesions to diminish in size

14. Somatotroph adenomas
The second most common type of functioning pituitary adenoma
They cause gigantism in children and acromegaly in adults
…GH effects here are mainly due to insulin-like growth factor
They may be quite large by the time they come to clinical attention because the manifestations of excessive GH may be subtle and slowly progressive over decades
Also classified as densely or sparsely granulated…don’t bother yourself
Bihormonal mammosomatotroph adenomas that synthesize both GH and prolactin are being increasingly recognized

15. In most instances gigantism is also
Especially skin, soft tissue, bone (esp., hands, feet & face) and viscera
protrusion (prognathism),
and broadening of the lower face
In most instances gigantism is also
accompanied by evidence of acromegaly

16. Other manifestations of GH excess
Treatment
The underlying pituitary adenoma can be either
removed surgically or treated via pharmacologic means.
The latter includes somatostatin analogs (recall that somatostatin inhibits pituitary GH secretion) or the use of GH receptor antagonists, which prevent hormone binding to target organs such as the liver

17. Corticotroph adenomas
Excess production of ACTH by functioning corticotroph adenomas leads to adrenal hypersecretion of cortisol and the development of hypercortisolism (also known as Cushing syndrome)…in this case we call it: Cushing disease
POMC is a precursor for ACTH and MSH…remember this
Usually detected when small (microadenomas)
If someone has an undetected corticotroph microadenoma and surgically treated by removal of both adrenals…What will happen?

18. Pituitary carcinomas
Rare, accounting for less than 1% of pituitary tumors
Metastasis
Most pituitary carcinomas are functional, with prolactin and ACTH being the most common secreted products

19. Hypopituitarism Due to pituitary or hypothalamic problem
Hypopituitarism accompanied by evidence of posterior pituitary dysfunction in the form of diabetes insipidus is almost always of hypothalamic origin (like a benign tumor called craniopharyngioma or other causes such as radiation or metastatic cancer (breast, lung…etc.)
Most cases of hypopituitarism arise from destructive processes directly involving the anterior pituitary:
-Any mass lesion in the sella can cause damage by exerting pressure on adjacent pituitary cells
-Traumatic brain injury and subarachnoid hemorrhage are among the most common causes of pituitary hypofunction
-Pituitary surgery or radiation
-Pituitary apoplexy
-Sheehan syndrome (postpartum ischemic necrosis of the anterior pituitary)…How does it occur?

20. Clinical manifestations of hypopituitarism

21. Posterior Pituitary Syndromes
Diabetes insipidus
Central: Head trauma, tumors, inflammatory disorders of the hypothalamus and pituitary, and surgical complications or
Nephrogeneic
…Polydipsia, polyuria with dilute urine
SIADH (syndrome of inappropriate ADH secretion)
Hyponatremia, cerebral edema and neurological dysfunction
Lung small cell carcinoma, drugs or CNS infections or trauma
Although total body water is increased, blood volume remains normal, and peripheral edema does not develop

22. Thank You