Endocrine Flashcards
Hormones secreted by acidphils of anterior pituitary
Growth hormone/somatotrophin (by somatotropes)
Prolactin/lueteotrophic hormone (by luteotrophs)
Hormones secreted by basophils of anterior pituitary
Thyroid stimulating hormone (thyrotrophs)
LH/FSH (gonadotrophs)
Hormones secreted by chromophobes of anterior pituitary
Adrenocorticotropic hormone
Melanocyte secreting hormone
Most likely cause of hyperfunction of pituitary gland
Neoplasm!
(Functional corticotroph adenoma - over production of ATCH by anterior pituitary)
Impact of excess cortisol
Changes due to:
Gluconeogenic, lipolytic, protein catabolic, anti-inflammatory action of glucocorticoids
Sequeale of corticorph adenoma
Compression, hemorrhage —> CNS damage
Cortical hyperplasia (by action of ACTH on adrenal glands)
Types of corticotroph adenoma / species predilection
Pars distalis adenoma (dogs)
Pars intermedia adenoma (horses, less commonly in dogs)
Equine pituitary pars intermedia dysfunction (PPID)
Adenoma of pars intermedia
Similar to Cushing’s of other animals
Autonomous production of POMC (pro-opiomelanocortin) peptides (inc in ACTH activity), loss of normal inhibitory control
Pathogenesis of PPID
Dec in dopamine which normally inhibits cells in pars intermediate
Loss of inhibition —> increased peptide synthesis
Hypertrophy + hyperplasia —> adenoma formation
Actions of POMC in PPID
In pars distalis —> ATCH, b=endorphin, b-lipotropin
In pars intermediate —> ACTH —> a-MSH, corticotrophin-like intermediate lobe peptide, b-MSH, b-endorphin
Plasma cortisol inhibits ATCH secretion by pars distalis (but little effect on pars intermedia)
Sequelae of adenoma of pars intermedia
Compression of hypothalamus —> deranged function
Compression —> fever, sweating, hirsutism
POMC —> inc ACTH activity —> Cushings-like disease
Clinical syndromes of PPID
Weight loss muscle weakness, atrophy
Increased susceptibility to infection / poor would healing
PU/PD, increase appetite, somnolence, intermittent fever
Hypertrichosis
(Hirsutism), long hair/hair overgrowth due to failure of seasonal shedding
Hyperhidrosis
Generalized sweating, excess sweating
Equine Cushings
Hypertrichosis/hirsutism
Hyperhidrosis
Laminitis
Functional acidophilus adenoma
Tumor of pituitary overproducing GH —> over production of tissue —> acromegaly
Feline acromegaly
Cardiomegaly+ enlargement of various organs (liver, kidney)
New bone deposition
Increased weight due to inc muscle/organ/bone mass
Respiratory stridor (due to thickening airy MM)
Severe, insulin-resistant DM due to GH-induced IR
Hypofunction of pituitary due to
Compressive disease (tumor, can cause neuro signs)
Trauma
Congenital defects
Nonfunctional pituitary tumors
Clinical signs due to compression, decrease in secretion of tropic hormones
Pituitary carcinoma
Usually nonfunctional, compressive, infiltrative
Diabetes insipidus
Hypophyseal form, hypofunction of pituitary gland
ADH in low levels from compression/destruction of neurohypophysis —> can not trigger increased water absorption in kidneys
Clinical manifestation: increased urine production
Nephrogenic DI
Target cells in kidney not responding to ADH
- congenital or acquired in animals with pyometra
Juvenile panhypopituitarism
Failure of differentiation of pharyngeal ectoderm —> undifferentiated cells produce fluid —> cysts in sella tursica —> absence of adnohypophysis
Pituitary dwarfism
Autosomal recessive in German Shepard (occasionallly in other dogs)
Clinical signs of panhypopituitarism
Slow growth, small stature
Failure to gain adult coat, delayed eruption of permanent teeth, delayed epiphyseal closure, infantile external genitalia
Due to growth hormone deficiency
Pituitary cysts
Relatively common finding in dogs
Often incidental
Cause of primary adrenal gland hyperfunction
Adrenocortical adenoma / carcinoma
Cause of secondary adrenal gland hyperfunction
Corticotroph adenoma in pituitary (PDH)
(Cushing’s syndrome)
Cause of hyperfunction of adrenal medulla
Pheochromocytoma
Causes of Cushing’s syndrome
Anterior pituitary tumor (inc in ACTH —> inc cortisol)
Adenocortical tumor (inc in cortisol)
Exogenous steroids (also produces adrenal atrophy)
Predilection based on cause of Cushing disease
PDH (pituitary tumor) - middle aged to older, Poodles, Dachshunds, German Shepard, boxers
AT (adrenocortical) - older female dogs
Signs of Cushings
Inc ALP
Pendulous abdomen, pot-belly
PU/PD (IN DOGS!)
Increased appetite
Hepatomegaly (steroid hepatopathy?)
Panting
Clinical manifestations of Cushings
Muscle atrophy
Alopecia, thin skin
Calcinosis cutis (mineralization of collagen in dermis)
Increased susceptibility to pathogens
Diabetes mellitus
Treatment of Cushings
Lysodren (mitotane) - controlled destruction of cortex (inhibits adrenal steroidogenesis, direct cytotoxic effect on adrenal cortex)
Trilostane - newer drug, blocks enzyme in steroidogenesis pathway
Cushings in cats
Rare
Concurrent with DM
No steroid hepatopathy
May have fragile skin (dermal atrophy)