Pathophysiology of the Pituitary Gland

Question 1

what secretes growth hormone releasing hormone?

Answer 1

hypothalamus

Question 2

what stimulates the hypothalamus to produce growth hormone releasing hormone?

Answer 2

ghrelin

Question 3

what is growth hormone important for?

Answer 3

glucose homeostasis
lipolysis
insulin secretion

Question 4

what is primary hypopituitarism?

Answer 4

deficiency of one or more pituitary hormones

Question 5

what are the two forms of primary hypopituitarism?

Answer 5

congenital: pituitary dwarfism
acquired: adult-onset

Question 6

who is primary hypopituitarism (pituitary dwarfism) most common in?

Answer 6

German Shepherds

Question 7

can primary hypopituitarism (pituitary dwarfism) be seen with other pituitary hormone deficiencies, including ACTH?

Answer 7

yes, but not with ACTH

Question 8

what are the causes of primary hypopituitarism (pituitary dwarfism)?

Answer 8

cystic dilation of rathke’s pouch
developmental failure of trophic cells
pituitary tumor

Question 9

what is the presentation of primary hypopituitarism?

Answer 9

failures of normal growth
clinically can mimic congenital hypothyroidism

Question 10

what are the clinical signs of primary hypopituitarism (pituitary dwarfism)?

Answer 10

dwarfing/short stature
abnormal haircoat
infantile genitalia
delayed closure of growth plates
delayed dentition
mental dullness

Question 11

what are some useful diagnostic aids for pituitary dwarfism?

Answer 11

comparison of height with littermates
radiographs of open epiphyseal lines
thyroid function tests
skin biopsy (mostly to rule out other causes of alopecia)
serum determination of: growth hormone, insulin-like growth factor-1 (a lot of labs do not measure)

Question 12

what are the laboratory findings of pituitary dwarfism?

Answer 12

usually pretty normal: things associated with being a tiny puppy

Question 13

what can cause primary hypopituitarism (adult-onset hypopituitarism)?

Answer 13

non-functional pituitary or other brain tumors
inflammation, thrombosis, trauma

Question 14

what are the clinical signs of primary hypopituitarism (adult-onset hypopituitarism)?

Answer 14

neurologic abnormalities
those of ADH, TSH, or ACTH deficiency

Question 15

pituitary dwarfism is familial in which dog breed?

Answer 15

german shepherds

Question 16

what can cause adult-onset hyperpituitarism?

Answer 16

functional micro or macroadenoma
pituitary-dependent hyperadrenocorticism

Question 17

what are the causes of hyperpituitarism in dogs?

Answer 17

other growth hormone-producing tumors: mammary, progesterone therapy, primary hypothyroidism
functional pituitary tumor (rare)

Question 18

what is the etiology of hyperpituitarism in cats?

Answer 18

growth hormone-secreting pituitary tumor

Question 19

who is most likely to get hyperpituitarism?

Answer 19

middle-aged to older animals
dogs: primarily females
cats: primarily males

Question 20

what is the pathophysiology of hyperpituitarism due to?

Answer 20

excessive growth hormone production

Question 21

what are the clinical signs of hyperpituitarism?

Answer 21

prominent skin folds of face and neck
blunt, broad head
enlarged chin, forehead, limbs, feet
enlarged interdental spaces
abdominal enlargement

Question 22

what organ enlargement does hyperpituitarism cause?

Answer 22

hepatomegaly
renomegaly
cardiomegaly
respiratory stridor: increase in upper airway soft tissue, macroglossia

Question 23

what is a complication of hyperpituitarism?

Answer 23

diabetes mellitus

Question 24

how can you diagnose acromegaly?

Answer 24

no singe diagnostic test: clinical signs associated with poorly-controlled type 2 diabetes mellitus
laboratory measurement of IGF-1
CT/MRI imaging of the pituitary gland

Question 25

what are the two types of central diabetes insipidus?

Answer 25

absolute partial

Question 26

what happens with complete central diabetes insipidus?

Answer 26

persistent hyposthenuria and severe diuresis despite dehydration

Question 27

what are the etiologies of central diabetes insipidus?

Answer 27

congenital infection trauma neoplasia idiopathic: most common

Question 28

what is the etiology of nephrogenic diabetes insipidus?

Answer 28

impaired responsiveness of the nephron to ADH: primary and secondary

Question 29

what are the clinical signs of diabetes insipidus?

Answer 29

severe polyuria/polydipsia dehydration neurologic signs

Question 30

what are the laboratory findings of diabetes insipidus?

Answer 30

increased serum osmolality decreased urine osmolality hyposthenuria inadequate water intake water deprivation test ADH-response test

Question 31

what are some laboratory abnormalities associated with inadequate water intake?

Answer 31

azotemia hypernatremia hyperproteinemia erythrocytosis

Question 32

how is an ADH-response test performed?

Answer 32

urine specific gravity is determined at the start of the test desmopressin acetate administered bladder emptied after 2 hours urine specific gravity measured at set intervals expect increased USG if responsive to ADH

Question 33

what can cause inappropriate release of ADH in absence of normal stimuli?

Answer 33

cerebral diseases pulmonary diseases idiopathic drug idiosyncrasies

Question 34

what happens in syndrome of inappropriate ADH secretion with decreased free water excretion?

Answer 34

volume expansion hyponatremia hypoosmolality

Question 35

what hormones are secreted by the anterior pituitary?

Answer 35

growth hormone prolactin ACTH thyrotropin stimulating hormone follicle stimulating hormone luteinizing hormone melanocyte stimulating hormone POMC

Question 36

what hormones are secreted by the posterior pituitary?

Answer 36

antidiuretic hormone oxytocin

Question 37

what does growth hormone do?

Answer 37

adipose: increases lipolysis and decreases glucose uptake liver (increases IGF-1): increases gluconeogenesis, glycogenolysis, gluconeogenesis (kidneys), decreases glucose uptake muscle: increases glycogenolysis, decreases glucose uptake pancreas: increases insulin secretion

Question 38

primary hypopituitarism can clinically mimic _________________________

Answer 38

congenital hypothyroidism

Question 39

what are some laboratory abnormalities associated with primary hypothyroidism/pituitary dwarfism?

Answer 39

mild anemia, hypophosphatemia, hypoalbuminemia azotemia due to decreased GFR hypercholesterolemia due to secondary hypothyroidism

Question 40

what is acromegaly from?

Answer 40

from hyperpituitarism

Question 41

which breed of cat is most likely to have hyperpituitarism?

Answer 41

domestic shorthairs

Question 42

what mediates growth hormone's effects on tissues?

Answer 42

insulin-like growth factor-1

Question 43

what are the anabolic effects of excessive growth hormone on tissues?

Answer 43

overgrowth of connective tissue, bone, viscera

Question 44

what are the metabolic effects of excessive growth hormone on tissues?

Answer 44

effects on glucose and insulin regulation

Question 45

how does hyperpituitarism lead to diabetes mellitus?

Answer 45

excess growth hormones results in downregulation of insulin receptors and resistance to the action of insulin at the target cell level

Question 46

what are the chemistry abnormalities associated with hyperpituitarism?

Answer 46

hyperglycemia hypercholesterolemia hyperproteinemia hyperphosphatemia

Question 47

what are the CBC abnormalities associated with hyperpituitarism?

Answer 47

erythrocytosis

Question 48

what are the urinalysis abnormalities associated with hyperpituitarism?

Answer 48

glucosuria

Question 49

how can we diagnose hyperpituitarism?

Answer 49

complicated: no single diagnostic test, looks similar to type 2 diabetes laboratory measurement of IGF-1: usually elevated, repeat in 3-6 months CT/MRI of the pituitary gland

Question 50

what happens with partial central diabetes insipidus?

Answer 50

persistent hyposthenuria and severe diuresis as long as the animal has access to water

Question 51

what is the most common cause of central diabetes insipidus?

Answer 51

idiopathic

Question 52

what causes primary impaired responsiveness of the nephron to ADH?

Answer 52

congenital

Question 53

what causes secondary impaired responsiveness of the nephron to ADH?

Answer 53

hyperadrenocorticism hypercalcemia therapy with outdated tetracyclines endotoxemia pyelonephritis

Question 54

why do animals with diabetes insipidus have neurologic signs?

Answer 54

pituitary tumor electrolyte abnormalities

Question 55

what are the laboratory findings associated with inadequate water intake with diabetes insipidus?

Answer 55

azotemia hypernatremia hyperproteinemia erythrocytosis

Question 56

what are the differential diagnoses for polyuria/polydipsia?

Answer 56

diabetes insipidus diabetes mellitus drugs hyperadrenocorticism hypoadrenocorticism hypercalcemia hypertension hyperthyroidism hyperviscosity hypokalemia liver disease pyelonephritis pyometra renal failure psychogenic

Question 57

what is syndrome of inappropriate ADH secretion?

Answer 57

inappropriate release of ADH in absence of normal stimuli: too much ADH

Question 58

what can cause syndrome of inappropriate ADH secretion?

Answer 58

cerebral diseases pulmonary diseases idiopathic drug idiosyncrasies

Question 59

what are the neurologic clinical signs of syndrome of inappropriate ADH secretion from?

Answer 59

neuronal sensitivity for electrolyte abnormalities: swelling brain tumor