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Medicine 1 VCS860 > Endocrine Disorders of the Pituitary Gland > Flashcards

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
Q

Diabetes Insipidus

Abnormal Hormone

A

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
Q

Anti-Diuretic Hormone

A

principal hormone involved in body water homeostasis

27
Q

Diabetes Insipidus

Pathogensis

Central Diabetes Insipidus (CDI)

A

results form deficient production of ADH

ADH deficiency may be complete or partial

28
Q

Diabetes Insipidus

Pathogensis

Causes fo CDI

Congenital

A

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
Q

Diabetes Insipidus

Pathogensis

Causes of CDI

Acquired

A

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
Q

Diabetes Insipidus

Clinical signs

A

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
Q

Diabetes Insipidus

Laboratory Findings

hydrated animals

A

results are generally normal

Mild hypernatremia is common, the result of mild water restriction

Urine specific gravity <1.008

32
Q

Diabetes insipidus

Laboratory findings

Dehydrated animals

A

hypernatremia is expected

Azotemia may be present

33
Q

Diabetes Insipidus

Laboratory Findings

Osmolality measurements

A

Comparison between plasma and urine osmolality is essential for confirming the diagnosis of CDI

Normal plasma osmolality is maintained within a narrow range

34
Q

Diabetes Insipidus

Differential Diagnoses

A

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
Q

Diabetes Insipidus

Differential DIagnoses

Primary Polydipsia

A

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
Q

Diabetes Insipidus

Differential Diagoses

Nephrogenic Diabetes Insipidus (NDI)

A

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
Q

Diabetes Insipidus

Differential Diagoses

Nephrogenic Diabetes Insipidus (NDI)

Congenital

A

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
Q

Diabetes Insipidus

Differential Diagoses

Nephrogenic Diabetes Insipidus (NDI)

Acquired

A

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
Q

Diabetes Insipidus

Confirming the diagnosis of CDI

A

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
Q

Diabetes Insipidus

Confirming diagnosis

Water Deprivation Test

A

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
Q

Diabetes Insipidus

Confirmind diagnsis

WDT
Protocol

A

there are severla published protocols. Many clinicians prefer the modified water deprivation test

42
Q

Treatment of CDI

A

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.

43
Q

Prognosis of CDI

A

Congenital CDI without progressive pituitary patholgy - GOOD

Acquired CDI caused by progressive pituitary patholgy - POOR

Medicine 1 VCS860 (13 decks)

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