Module 1: Pituitary Pathology and Pathophysiology Flashcards
The anterior pituitary (adenohypophysis) is composed of two histologically and functionally distinct regions:
the pars distalis and the pars intermedia
there are three morphologically distinct cells within the pars distalis:
acidophils, basophils, and chromophobes
it lacks the secretory polygonal cells characteristic of the anterior pituitary
posterior pituitary, or pars nervosa
Are transported along the axons into the pars nervosa where they are secreted and enter the bloodstream
anti-diuretic hormone (ADH; also referred to as vasopressin) and oxytocin
specialized supporting cells (glial cells) of the pars nervosa that surround the axons and facilitate secretion of ADH and oxytocin
Pituicytes
is composed predominantly of anuclear (without nuclei) axons and small capillaries, scattered nuclei are apparent within the neuropil; these are pituicytes
pars nervosa
What are the clinical disease of functional neoplasms?
effects of overproduction
of trophic hormones +/- expansile or infiltrative effects
What are the clinical disease of Non-functional neoplasms?
expansile or
infiltrative effects (tissue loss/destruction)
What are the Clinical Signs of Equine pituitary pars intermedia dysfunction (PPID)?
Clinical signs primarily due to compression of normal
pituitary/hypothalamus (although some increased ACTH, POMC, MSH,
β-END)
Not really a functional tumor
• Develop in older horses (females>males)
• Clinical signs
• PU/PD
• Polyphagia
• Hirsutism (hairy coat)
• Laminitis
• Muscle weakness/atrophy
• Hyperhidrosis
• May develop insulin-resistant hyperglycemia
• Diabetes insipidus
PPID (Equine pituitary pars intermedia dysfunction)
Most of Pituitary tumors in domestic animals are ________
Benign
• Clinical signs primarily due to effects of cortisol excess
• Common in dogs (less common in cats)
• Size does not correlate with functional activity
• Bilateral adrenal cortical hyperplasia
ACTH-secreting adenomas (pars distalis»_space;> pars intermedia)
Functional tumor
• Clinical signs primarily due to cortisol excess (adrenal cortisol
hypersecretion)
• Polyuric/polydipsic
• Symmetric alopecia (truncal)
• Pot-bellied appearance – loss of abdominal musculature
• Calcinosis cutis – mineralization of dermal collagen
• Hypercoagulability (pulmonary thromboemboli)
Canine Cushing’s disease
(Pituitary adenoma of the pars distalis (80%))
• Most commonly prolactin-secreting adenomas
• Prolactin may induce mammary neoplasia in rats
• Associated with mammary fibroadenomas – benign mammary tumors
Pituitary adenoma of the pars distalis in Rats
Pituitary adenomas and mammary tumors in rats are associated with
increased _______________
caloric intake
• Pituitary tumors are common in this species
• Neurological signs (ataxia, difficulty
flying, head tilt, abnormal molting)
• Growth hormone secreting
• Many are malignant and may metastasize
Pituitary adenomas in Budgerigars (parakeets)
• Uncommon
• Primarily prolactin-secreting
• Frequently clinically asymptomatic
Pituitary adenomas in Cynomolgus macaques
when you have a short supply (deficiency) of one or more of the pituitary hormones
Hypopituitarism
Hypopituitarism
• Two basic pathogeneses:
- Congenital absence (primary hypopituitarism)
- Acquired destruction of pituitary (secondary hypopituitarism)
• Rare diseases (mostly canine)
• Juvenile animals affected
primary hypopituitarism
• Neoplasia (primary vs. metastatic)
• Pituitary abscesses
secondary hypopituitarism
• Autosomal recessive inheritance in German shepherd dog, Karelian
bear dog, Spitz, et al
• DNA repeat of intron 5 of LHX3 gene
• Failure of Rathke’s pouch to differentiate into the pars distalis
• Abnormal development leads to cyst formation →expansile mass and
compression/destruction of remaining functional pituitary tissue
Primary hypopituitarism (Juvenile-onset panhypopituitarism,
piutuitary dwarfism)
• Clinical appearance
• Major clinical signs associated with reduced/absence of:
• Growth hormone (GH)
• Thyroid stimulating hormone (TSH)
• Adrenocorticotrophic hormone (ACTH)
• Gonadotrophic hormones (LH, FSH)
• Key point: Without upstream stimulation by the pituitary gland’s trophic hormones, there is reduced production of the downstream hormones (i.e. thyroxine, somatomedin, cortisol, sex hormones)
• Affected dogs have small stature, lack guard hairs (puppy coat), significantly delayed physeal closure, alopecia, atrophic skin, etc.
• Diagnostic test for insulin-like growth factor (somatomedin) is available (MSU VDL)
Juvenile-onset hypopituitarism
• Acquired loss of pituitary function
• Infectious
• Pituitary abscess
• Cattle, small ruminants
• Clinical signs dependent on degree of pituitary destruction +/-
compression/destruction of regional brain (may be acute or chronic)
• Hematogenous spread»_space; regional extension
• Uncommonly, may be associated with skull fracture/penetrating wound, otitis media,
or tooth root abscess
Secondary hypopituitarism
