Pituitary Pathology Flashcards
What do the pink acidophils of the pituitary gland secrete?
Growth hormone and prolactin
What do the dark purple basophils secrete?
Corticotropin (ACTH)
TSH
Gonadotrophins (FSH and LH)
What hormones does the adenohypophysis secrete?
Six hormones:
1. ACTH
2. FSH
3. GH
4. LH
5. PRL
6. TSH
What are the stimulatory releasing factors that the anterior pituitary hormones are under control of?
Corticotropin-releasing hormone (CRH)
GHRH
Gonadotropin-releasing hormone (GnRH)
TRH
What are the inhibitory releasing factors that the anterior pituitary hormones are under control of?
Growth inhibitory hormone (Somatostatin)
Prolactin inhibitory factor (Dopamine)
What is the population of pituitary adenomas?
ADults 35 to 60 years of age
How are pituitary adenomas classified?
Based on hormone production (Functional & Non-functional)
According to size
What are micro adenomas?
Less than 1 cm
What are macro-adenomas?
More than 1cm
What is the pathogenesis of sporadic pituitary adenoma?
- Activating mutation in the GNAS (G protein mutation) –> that interferes with its intrinsic GTPase activity
- Constitutive activation of Gs(a) and adenylate cyclase, persistent generation of cAMP (potent mitogen)
- Stimulate hypersecretion and cell proliferation (mainly GH adenoma)
What is the % of familial pituitary adenoma?
5%
What are the different types of familial pituitary adenomas?
- Multiple Endocrine Neoplasia Type 1 (MEN-1)
- Carney Complex Syndrome
- Familial Isolated Adenomas (FIPAs)
- Mutations of Cyclin-Dependent Kinase Inhibitor 1B
What is the Carney Complex Syndrome?
Mutation in the gene for protein kinase A regulatory subunit I a (PRKAR1A)
What does Carney Complex Syndrome result in?
Acromegaly (GH & prolactin secretion)
What are familial isolated adenomas?
Mutation in aryl hydrocarbon receptor-interacting gene (AIP)
What is the result of familial isolated adenomas?
Develop GH-secreting adenomas at a younger age (before the age of 35)
WHat are mutations of cyclin-dependent kinase inhibitor 1B?
CDKN1B gene is the cell cycle checkpoint regulator p27 or KIP1 –> aggressive adenoma (Cyclin D1, TP53, RB)
What is the gross anatomy of small lesion pituitary adenomas?
Well-circumscribed, soft lesions
What is the gross anatomy of large lesion pituitary adenomas?
- They compress the optic chiasm and adjacent structures (extend locally into the cavernous and sphenoidal sinuses)
- Foci of hemorrhage and/or necrosis are common in larger adenomas
What are the microscopic features of pituitary adenomas?
- Cellular monomorphism of one cell type
- Absence of a significant reticulin network
- Hemorrhage and necrosis may occur
- Rare mitosis
What is the growth pattern of the pituitary adenomas?
Diffuse trabecular, pseudo-acinar or psedo-papillary
What is used for hormonal identification of pituitary adenomas (microscopically)?
Immunohistochemistry (IHC)
What are the symptoms of the pituitary adenomas?
Local mass effects
Hyperpituitarism
Hypopituitarism
What are the radiographic abnormalities of the sella turcica in the local effects of pituitary adenomas?
Sellar expansion
Bony erosion
Disruption of the diaphragma sellae
What are the mass effects of pituitary adenomas?
Local effects
Compress decussating fibers in the optic chiasm
Elevated intracranial pressure
Invasive pituitary adenoma
Acute hemorrhage
What is the effect of compressing decussating fibers in the optic chiasm?
Bitemporal hemianopsia (defects in the lateral visual fields –> tunnel)
What are the effects of elevated intracranial pressure?
Expanding intracranial mass:
1. Headache
2. Nausea and vomiting
What are the effects of invasive pituitary adenomas?
They extend beyond the sella turcica:
1. Seizures
2. Obstructive hydrocephalus
3. Cranial nerve palsy (involvement of cranial nerves)
What is the effect of acute hemorrhage (pituitary apoplexy)?
Rapid enlargement of the lesion –> loss of consciousness –> sudden death (neurological emergency)
What is hypepituitraism?
Excessive secretion of trophic hormones (FSH, LH, ACTH, TSH)
What are the causes of hyperpituitarism?
Anterior pituitary adenoma (most common)
Pituitary hyperplasia (less common)
Pituitary carcinoma and hypothalamic causes (even less common)
What is the effect of pituitary hyperplasia?
Secretion of hormones by extra pituitary site
What are the types of functioning adenomas pituitary cell types?
- Corticotroph
- Somatotroph
- Lactotroph
- Mammosomatotroph
- Thyrotroph
- Gonadotroph
What are the hormones associated with corticotrophin?
ACTH and other POMC-derives peptides
What is the type of tumor associated with corticotrophs?
ACTH cell (corticotroph) adenoma
What are the associated syndromes with corticotroph tumors?
Cushing’s syndrome
Nelson syndrome
What are the hormones associated with somatotrophs?
GH
What is the type of tumor associated with somatotrophs?
GH cell (somatotroph) adenoma
What are the associated syndromes with somatotroph tumors?
Gigantism (children)
Acromegaly (adults)
What are the hormones associated with lactotrophs?
Prolactin
What is the type of tumor associated with lactotrophs?
Prolactin cell (lactotroph) adenoma
What are the associated syndromes with lactotroph tumors?
Galactorrhea and amenorrhea (in females)
Sexual dysfunction, infertility
What are the hormones associated with mammosomatotrophs?
Prolactin
GH
What is the type of tumor associated with mammosomatotrophs?
Mammosomatotroph
What are the associated syndromes with mammosomatotroph tumors?
Combined features of GH and Prolactin excess
What are the hormones associated with thyrotrophs?
TSH
What is the type of tumor associated with thyrotrophs?
TSH cell (thyrotroph) adenoma
What are the associated syndromes with thyrotroph tumors?
Hyperthyroidism
What are the hormones associated with gonadotrophs?
FSH
LH
What is the type of tumor associated with gonadotrophs?
Gonadotroph, “null cell” oncocytic adenomas
What are the associated syndromes with gonadotroph tumors?
Hypogonadism, mass effects, and hypopituitarism
What is a prolactinoma?
The most common type of pituitary adenoma, it is a tumor of lactotroph cells
Who is more likely to get affected by prolactinomas?
Females > Males
Age 20 to 50
What are the effects of female prolactinoma microadenoma? (< 10mm)
Galactorrhea
Amenorrhea
Infertility
What are the effects of male prolactinoma macroadenoma (>10mm)?
Decreased libido,
Gynecomastia,
Infertility
What is the male and female mass effects of prolactinomas?
Headaches,
CSF rhinorrhea,
Compression of optic chiasma & optic nerve
What are the functions of prolactin?
- Stimulates milk production in breast
- Inhibits ovulation in females and spermatogenesis in males by inhibiting GnRH synthesis and release
- Excessive amount associated with decreased libido
What inhibits prolactin?
Dopamine
Dopamine agonists
What does prolactin inhibit?
Its own secretion by dopamine synthesis and secretion from hypothalamus
Which hormone affects prolactin secretion positively?
TRH (primary or secondary hypothyroidism for example)
What is an example of a dopamine agonist?
Bromocriptine
What substances stimulate prolactin secretion?
Dopamine antagonists
Estrogens
What are examples of dopamine antagonists?
Antipsychotics
What are examples of estrogens?
Oral contraceptives
Pregnancy
What is the diagnosis of prolactinoma?
Serum prolactin level > 200mcg/L
Radiology CT or MRI
What are other causes that could have led to an increase in serum prolactin levels?
- Renal failure
- High dose estrogen
- Pregnancy
- Hypothyroidism
- Hypothalamic lesions
- Dopamine inhibiting drugs
How does renal failure increase prolactin levels?
Urea toxic effects on hypothalamus –> decrease in dopamine, which inhibits the secretion of prolactin
What is the treatment for prolactinomas?
Medical: dopamine agonist (to suppress prolactin and shrink tumor)
Surgical: in the case that medical treatment fails, sometimes followed by RT
What are the microscopical findings of prolactinomas?
- Chromophobic in staining (sparsely granulated) & acidophilic (densely granulated)
- Spheroid nuclei
- Prominent nucleolus
- Sometimes, endocrine amyloid
- Psammoma bodies
What are growth hormone adenomas?
2nd most common
Tumour of somatotroph cells
What may adenomas produce?
A mixture of growth hormone and other hormones (like prolactin for instance)
What are the mutations of growth hormone adenomas?
40% have activated GNAS gene on chromosome 20q13 –> G protein –> continue cAMP production & cell proliferation
What is the result of persistent growth hormone?
Stimulates the hepatic secretion of insulin-like growth factor 1, which acts in conjunction with growth hormone to induce overgrowth of bone and muscles
What are the clinical features of growth hormone adenoma?
Gigantism in children
Acromegaly in adults
What is gigantism?
Generalized increase in body size, with dispospprtioately long arms and legs
What is acromegaly? (5)
- Growth in soft tissues, skin, and viscera and in the bones of the face, hands, and feet
- Enlarged jaw with broadening of the lower face and enlarged tongue and teeth separation
- Hands and feet are enlarged, with broad, sausage-like fingers
- Secondary DM
- Muscle weakness, HTN, arthritis, osteoporosis, and Biventricular hypertrophy
What tumors’ risk increases with Acromegaly?
GIT tumours
What are the diagnostic criteria for Growth hormone adenoma? (4)
- Increase in growth levels
- Increase in IGF-1
- Lack of GH suppression by oral glucose
- Radiology CT or MRI
What are the treatment methods for growth hormone adenomas?
Somatostatin (suppressed GH)
Surgery
what are the microscopical findings of growth hormone adenoma?
Densely granulated form composed of acidophilic cells
Sparsely granulated variety that features chromophobic cells
What are adenocorticotrophic hormone-producing adenomas?
they secrete ACTH, leading to Cushing’s disease
Associated with hyperpigmentation (increase in MSH, derived from the same precursor as ACTH)
What are adenocorticotrophic hormone-producing adenomas like at the point of diagnosis?
Microadenomas
How do adenocorticotrophic hormone-producing adenomas stain?
Stain positively with periodic acid-Schiff stains because of the accumulation of glycosylated ACTH protein)
Secretory granules can be detected by IHC methods
What are non-functioning adenomas?
Null cell adenomas, usually macroadenomas, later presentation as no hormones
Hypopituitarism as it destroys adjacent pituitary parenchyma
What do non-functioning adenomas present by usually?
Mass Effect
What is hypopituitarism?
Insufficient hormone production by the anterior pituitary,
It can be a deficiency in one hormone, several hormones, or complete pituitary failure
When do symptoms of hypopituitarism arise?
When > 75% of pituitary parenchyma is lost
What are the causes of hypopituitarism?
- Mass Effect by a pituitary tumor in adults and craniopharyngioma in children
- Bleeding in pituitary tumour
- Ischemic necrosis as Sheehan syndrome, or DIC, increase in IPC, trauma/shock and SCA
- Ablation of the pituitary gland by surgery or irradiation
- Empty sella syndrome
- Inflammatory lesions
- Metastatic tumours
- Hypothalamic tumors
- Growth hormone insensitivity
- Hemochromatosis
What is Sheehan syndrome?
Pregnancy-related infraction (gland size enlarged in pregnancy but blood supply does not, blood loss during childbirth) –> present poor lactation, loss of pubic hair, fatigue, and other features
What is empty sella syndrome?
Congenital or acquired by herniation of arachnoid & CSF into sella compresses and destroys the pituitary gland, especially in obese women
What is an example of growth hormones insensitivity?
Laron Dwarfism –> AR due to abnormality of GH receptor
What are the clinical features of hypopituitarism? (GH deficiency in children)
Growth failure (pituitary dwarfism)
What are the clinical features of hypopituitarism? (Gonadotrophin or GnRH deficiency)
Female: amenorrhea and infertility
Male: decreased libido, impotence, and loss of pubic and axillary hair
What are the clinical features of hypopituitarism? (TSH and ACTH deficiencies)
Hypothyroidism and hypoadrenalism
What are the clinical features of hypopituitarism? (Prolactin deficiency)
Failure of postpartum lactation
What are the clinical features of hypopituitarism? (Loss of stimulatory effects of MSH on melanocytes)
Pallor
What are the hormones of the posterior pituitary gland?
ADH and Oxytocin
Where does ADH function?
Acts on the kidney distal tubule and collecting ducts and promotes retention of water
Where does oxytocin fucntion?
Mediates uterine contractions during labor and milk release in lactating mothers
What are the stimulating factors of ADH?
Plasma oncotic pressure
Exercise
Decrease in blood volume
Emotional state
How does a decrease in blood volume increase ADH stimulation?
Decrease in blood volume –> filling of atria –> stretch receptors not stimulated –> no inhibitory signal to the brain –> increase ADH secretion
What is diabetes insipidus?
ADH deficiency (central or cranial DI) or impaired renal response to ADH (nephrogenic ADH)
What are the characteristics of diabetes insipidus?
Inability to concentrate urine and consequent chronic water diuresis
What are the clinical features of diabetes insipidus? (6)
Due to loss of free water:
1. Polyuria
2. Thirst
3. Polydypsia & dehydration
4. postural hypotension
5. Increased serum osmolality and hypernatremia
6. Urien is diluted with low sepcific gravity
What are the causes of central DI? (7)
- Idiopathic
- Brain tumours
- Head injuries
- Brain malformation
- Infections (meningitis, encephalitis, TB)
- Surgery
- Radiotherapy
What are the causes of nephrogenic DI? (4)
- Drugs (lithium)
- Genetic (AVPR2 gene)
- Intrinsic Kidney Disease
- Electrolytes (hypokalemia, hypercalcemia)
What are the diagnostic criteria for DI?
Increased serum osmolality and Na
Decreased urine osmolality and low specific gravity
What is the syndrome of inappropriate ADH secretion (SIADH) ?
Excess ADH secretion
What are the effects fo SIADH?
- Retention of water –> hyponatremia and low serum osmolality
- Hyponatremia –> neuronal swelling and cerebral edema –> mental hanges and seizures
What is the blood volume like in SIADH?
Normal blood volume and no peripheral edema
What are the causes of SIADH? (4)
- Ectopic production (Lung small cell carcinoma)
- CNS trauma, stroke, infection, and tumors
- Pulmonary infections & COPD
- Drugs (cyclophosphamide, antipsychotic, NSAIDs)
