Endocrine Disorders of the Pituitary Gland Flashcards

1
Q

Acromegaly

A

aka Hypersomatotrophism

Chronic excessive growth hormone secretion which leads to overgrowth of connective tissue, bones, and viscera as well as insulin resistance

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2
Q

Acromegaly

Incidence

A

rare in cats and dogs

Canine acromegaly is exceedingly are in countries where OVH is an acceptable procedufe and most female dogs are spayed at a young age

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3
Q

Acromegaly

Etiology

A

Although increased circulating GH is a common feature of ACRO in cats and dogs, the source of GH is different in dogs and cats

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4
Q

Acromegaly

Etiology

Cats

A

caused by a GH producing pituitary tumor

Usually a macroadenoma of somatrotropic cells in the pars distalis

most common cause in people

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5
Q

Acromegaly

Etiology

Dogs

A

Caused by endogenous or exogenous progestins

Increased progesterone concentration occurs in older intact bitches during diestrus or in bitches given progesterone for estrus control

Progesterone in the dog is a stimulus for GH release

Pituitray GH-secreting adenoma is documented in dogs but should be considered extremely rare

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6
Q

Acromegaly

Signalment

A

affected dogs are typically older, intact females in spontaneous form, or any age with MPA treatment

Affected cats are usually geriatric males, although acro has been seen in cats as young as 4 years old

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7
Q

Acromegaly

History

Cats

A

affected cats usually present with polyuria, polydipsia, and polyphagia and overt diabetes mellitus

Weight loss may not be easily appreciated as the catabolic effects of diabetes are offset by the anabolic effects of GH

Less commonly recognized signs include: increased in body size, behavioral change, and respiratory distress

Neurologic signs related to the presence of the tumor may also be apparent at diagnosis

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8
Q

Acromegaly

Physical Exam

Cat

A

Physical changes nearly pathognomonic and include:

increase in the adult body size, especially muscle mass

Face is broadened and the jowls are prominent

Mandible protrudes and the interdental space is increased

Paws, limbs, and head are enlarged and the abdomen is distended.

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9
Q

Acromegaly

Diagnostics

CBC

A

results are non-specific: erythrocytosis seen in some cats

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10
Q

Acromegaly

Diagnostics

Chemistry

A

changes consistent with diabetes mellitus:

hyperglycemia, hypercholesterolemia, elevated alanine transferase ALT, and ALP

Hyperglobulinemia

Hyperphosphotemia without azotemia

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11
Q

Acromegaly

Diagnosis

Urinalysis

A

Proteinura

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12
Q

Acromegaly

Diagnostic imaging

A

needed when planning radiation therapy.

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13
Q

Acromegaly

Radiographs

A

increase in soft and bony tissues and organ enlargement

diffused enlargement of soft tissues of the head, neck, periarticular periosteal proliferation, elongated manible, hyperostosis of hte skill, cardiomegaly, renomegaly, hepatomegaly

Pulmonary and pleural changes may be seen in cases of cardiac failure

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14
Q

Acromegaly

Ultrasound

A

hepatomegaly is observed in about 50% of cats.

Echo changes consistent with lipid infiltrate

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15
Q

Acromegaly

CT or MRI

A

MRI: positive for a pituitary mass in most cats with ACRO, contrast useful in tumor detection

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16
Q

Acromegaly

Growth Hormone Assessment

A

Ideally, diagnosis would be accomplished this way.

Reliable, Commercial GH assays are not readily available for dogs or cats

Baseline GH levels are variable and depend on the point during the development of ACRO when measurement

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17
Q

Acromegaly

Insulin-like Growth Factor (IGF-1)

A

IGF-1 produced by the liver in response to GH.

Serum levels reflect GH secretion in the previous 24 hours

Unfortunately, some poortly-regulated diabetic cats also have elevations in IGF-1 in a range that overlaps with that seen in cats with ACRO

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18
Q

Acromegaly

Differential diangosis

Cats

A

Unregulated diabetes/insulin resistance

poorly regulated diabetes

feline hyperadrenocorticism

Prolonged administration of steroids or progestins

Severe hyperthyroidism

19
Q

Acromegaly

Differential Diagnoses: Cats

ACRO vs. Hyperadrenocorticism

A

Hyperadrenocorticism is a debilitating disease in cats and is associated with weight loss, and suppressed appetitie

Important distiniguishing feature of hyperadrenocorticism is the dermal atrophy that develops

20
Q

Acromegaly

Treatment

Cats

Radioation Therapy

A

TREATMENT OF CHOICE

resutls of cobalt RT have been mixed with some cats experiencing a marked decrease in the size fo the mass, while others show no response.

Improvement may take up to 6 months after RT

Diabetes abates in some cats but often recurs many months after RT

21
Q

Acromegaly

Treatment

Cats

Surgery

A

Currently, not an option

22
Q

Acromegaly

Treatment

Cats

Medical Management

A

Medical therapy should be considered palliative as no medical cure for ACRO is available

Adjunct medical therapy is directed at controlling diabetes and other associated disorders

23
Q

Acromegaly

Prognosis

Cats

A

Short term prognosis is usually good, particularly for cats taht present early in the course of hte disease, have no associated cardiac or renal failure.

Long term prognosis is poor

Reported survival ranges form 4 to 60 months but is typically 18-36 months

24
Q

Diabetes Insipidus

A

Disorder associated with production of copious amounts of urine (Polyuria)

RARE disorder in dogs and cats

Central DI has 3 characteristics: Dilute urine produced in the face of strong osmotic stimulation, occurs without renal disease, Exogenous vasopressin increased urine osmolality

25
Diabetes Insipidus Abnormal Hormone
Pituitary hormone called the Anti-Diuretic Hormone (ADH) or arginine vasopressin (AVP) produced by neurons originating in the hypothalamus. neuronal axons extend to the posterior pituitary, where secretion of ADH occurs ADH release determined by plasma osmolality.
26
Anti-Diuretic Hormone
principal hormone involved in body water homeostasis
27
Diabetes Insipidus Pathogensis Central Diabetes Insipidus (CDI)
results form deficient production of ADH ADH deficiency may be complete or partial
28
Diabetes Insipidus Pathogensis Causes fo CDI Congenital
Presumably caused by a genetic defect, but no specific gene defect has been identified in dogs. However, conceivable that developmental abnormalities might produce similar signs through non-genetic mechanisms Affected patients will demonstrate signs from birth
29
Diabetes Insipidus Pathogensis Causes of CDI Acquired
Anything that results in destruction of the posterior pituitary or serves the pituitary stalk can cause CDI Intracranial tumor - pituitary neoplasm most common Metastatic lesions Inflammatory infiltration Infection Severe Head Trauma Pituitary Surgery
30
Diabetes Insipidus Clinical signs
Excessive thirst (polydipsia) - constant desire and demand for water Excessive production of dilute urination (polyuria) - urine volume is large and the frequency of urination is increased Associated signs: Encephalopathy: denied water, animals with CDI rapidly develop life-threatening hypernatremia and dehydration. Hypernatremia is associated with encephalopathy that is manifest as mental dullness, ataxia, coma Animals with acquired CDI may exhibit signs assocaited with the initiating pathology
31
Diabetes Insipidus Laboratory Findings hydrated animals
results are generally normal Mild hypernatremia is common, the result of mild water restriction Urine specific gravity \<1.008
32
Diabetes insipidus Laboratory findings Dehydrated animals
hypernatremia is expected Azotemia may be present
33
Diabetes Insipidus Laboratory Findings Osmolality measurements
Comparison between plasma and urine osmolality is essential for confirming the diagnosis of CDI Normal plasma osmolality is maintained within a narrow range
34
Diabetes Insipidus Differential Diagnoses
what else causes polyuria Most commonly occuring disorders are readily ruled out by physical examination and minimal laboratory evaluation Primary (psychogneic) polydipsia Nephrogenic Diabetes insipidus
35
Diabetes Insipidus Differential DIagnoses Primary Polydipsia
This is a behavioral disorder Affected dogs drink excessive amounts of water and manifest polyuria as a physiological response to supraphysiological water intake Clinical signs: hyperactive, young dog There is a commonly a history of confinement, extended periods where the dog is un-stimulated or may become bored, or environmental/physical stress that precedes the onset of clinical signs
36
Diabetes Insipidus Differential Diagoses Nephrogenic Diabetes Insipidus (NDI)
patient have normal production and secretion of ADH. NDI is characterized by renal insensitivity to ADH, which causes impaired water reabsorption and results in the production of dilute urine
37
Diabetes Insipidus Differential Diagoses Nephrogenic Diabetes Insipidus (NDI) Congenital
extremely rare in dogs and cats, with only a handful of documented cases Present polyuria from birth and have historical, physical and clinical findings similar to animals with congenital CDI
38
Diabetes Insipidus Differential Diagoses Nephrogenic Diabetes Insipidus (NDI) Acquired
occurs in dogs and cats but the specific diagnosis is difficult to confirm and is usually not pursued. Acquired NDI develops secondary to another process
39
Diabetes Insipidus Confirming the diagnosis of CDI
In interpreting diagnostics tests, it must be noted that normal dogs have large fluctuations in urine osmolality and urine specific gravity. The work-up of animals with suspected DI/Primary Polydipsia shoeld begin with quantitation of water intake ands serial measurements of urine osmolality/USG.
40
Diabetes Insipidus Confirming diagnosis Water Deprivation Test
most common test for differentiating causes of polyuria but is fraught with problems Difficult to perform and interpret, potentially dangerous for hte patient, and should be considered only in very specific circumstances As a rule of thumb, if you find yourself contemplating doing a WDT on a patient - THINK AGAIN
41
Diabetes Insipidus Confirmind diagnsis WDT Protocol
there are severla published protocols. Many clinicians prefer the modified water deprivation test
42
Treatment of CDI
DDAVP Intranasal formation - one drop every 12 hours instilled itnot the conjunctival sac is sufficient dose for most affected animals. More frequent administration may be needed for full control.
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Prognosis of CDI
Congenital CDI without progressive pituitary patholgy - GOOD Acquired CDI caused by progressive pituitary patholgy - POOR