Digestion & Metabolism 2: Thyroid Diseases Flashcards
what is COLLOID?
COLLOID is present in THYROID & acts as PRECURSOR of THYROID HORMONES
FORMATION of THYROID HORMONES comes from ____ which we get through ____
formation is FACILITATED by WHAT enzyme? this is important because…
IODINE, DIET
ENZYME = THYROID PEROXIDASE
–> IMPORTANT because we can TARGET THIS ENZYME with DRUGS to SUPPRESS THYROID PEROXIDASE in HYPERTHYROIDISM
MOST of T3 and T4 in PLASMA will be….
when ACTIVATED…
BOUND TO PROTEINS in PLASMA
when PHYSIOLOGICALLY ACTIVATED, T3 and T4 ARE FREE
T____ is MORE active than T____
T3 is made in ___ by…
if we want to measure the ACTION of thyroid, we should measure…
T3 MORE ACTIVE THAN T4
T3 is made in PERIPHERY by DEIODINATION of T4
if we want to measure ACTION of thyroid = T4
NEGATIVE FEEDBACK cascade of THYROID? (5 steps)
- hypothalamus makes TRH
- stimulates PITUITARY to make TSH
- TSH acts on THYROID GLAND –> makes T3/T4
- LIVER makes PROTEINS BOUND TO MOST OF T3/T4
- but only T3/T4 FREE can cause NEGATIVE FEEDBACK
thyroid MAIN FUNCTION?
why can we see ANEMIA in HYPOTHYROIDISM
= INCREASE METABOLISM
anemia? = because THYROID INCREASES EPO PRODUCTION, so HYPOTHYROID = NOT ENOUGH EPO
5 MAIN thyroid hormone actions?
- STIMULATES PROTEIN SYNTHESIS
- STIMULATES CARB & LIPID METABOLISM
- STIMULATES EPO (making RBCs)
- STIMULATES BONE TURNOVER
- STIMULATES NEURAL & SKELETAL DEVELOPMENT
HYPERTHYROID DZ..
= definition?
commonality dogs vs. cats?
what AGE animals do we tend to see this in?
MOST COMMONLY caused by ___ ____, but possible to be caused by ___ yet this is ___
= CLINICAL CONDITION resulting from EXCESS PRODUCTION of T3/T4 by thyroid
CATS»_space;»> DOGS
tend to see in MIDDLE AGE-OLD CATS
MOST COMMONLY caused by ADENOMATOUS HYPERPLASIA, but possible to be caused by CARCINOMA but this is RARE
T4 name?
T3 name?
T4 = THYROXINE
T3 = TRIIODOTHYRONINE
ADENOMATOUS HYPERPLASIA of the THYROID…
most common cause of…
see grossly..
MOST COMMON CAUSE OF HYPERTHYROIDISM
see MULTIFOCAL NODULES THROUGH GLAND
ID LESION & DZ
ADENOMATOUS HYPERPLASIA
HYPERTHYROIDISM
MOST cats that become HYPERTHYROID are >____ ____
> 8 YEARS
HYPERTHYROIDISM…
1 common & often MISTAKEN clinical sign? how do owners see this?
6 other clinical signs?
1 common clinical signs? = POLYPHAGIA
–> owners MAY NOT NOTICE ANYTHING
other clinical signs?
1. WEIGHT LOSS despite RAVENOUS
2. PU/PD
3. V+
4. D+
5. POOR COAT
6. BEHAVIOR CHANGES
PE on HYPERTHYROIDISM? (4)
WHAT IS THE MOST IMPORTANT????
- HYPERACTIVE/hard to examine
- THIN
- ABNORMAL CARDIAC AUSCULTATION
- PALPABLE THYROID GLAND!!!! MOST IMPORTANT
three CBC abnormalities in HYPERTHYROIDISM?
however, they’re OFTEN ____ seen
- MILD elevation in PCV
- INCREASED MCV
- STRESS LEUKOGRAM
however, they’re OFTEN NOT seen
CHEMISTRY changes in HYPERTHYROIDISM? (3)
what 2 VALUES can be ELEVATED if CONCURRENT RENAL DZ?
- ALP/ALT elevation
- HYPERGLYCEMIA from STRESS
- T4 HIGH
2 elevations in CONCURRENT RENAL DZ?
1. BUN
2. CREATININE
diagnosis to CONFIRM HYPERTHYROIDISM?
if this test result is NORMAL but we still SUSPECT DZ, what should we do?
if STILL NORMAL, then likely…
TOTAL T4 CONCENTRATION!!
if we still SUSPECT DZ, then REPEAT 1-2 WEEKS since HORMONE LEVELS FLUCTUATE
if STILL NORMAL, then likely NONTHYROIDAL ILLNESS
FREE T4 CONCENTRATION…
this CANNOT be used as a ___ test for HYPERTHYROIDISM
why?
SINGLE
can be ELEVATED FOR OTHER REASONS
THYROID SCINTIGRAPHY…
helps ID what?
in HYPERTHYROIDISM, can help find ___ ___
helps ID FUNCTIONAL THYROID TISSUE
in HYPERTHYROIDISM, can help find ECTOPIC TISSUE
THREE DIAGNOSTICS we should perform for FELINE HYPERTHYROIDISM?
what 2 diagnostics can we reserve if ___ ___ is NORMAL?
- TOTAL T4
- CBC/CHEMISTRY
- UA
what 2 can we reserve if TOTAL T4 is NORMAL?
1. THYROID SCINTIGRAPHY
2. T3 SUPPRESSION TEST
BEFORE treating, need to ask WHAT QUESTION?
the answer in HYPOTHYROIDISM should be…
DO I NEED TO TREAT OR NOT?
IN HYPOTHYROIDISM, SHOULD ALWAYS BE YES
HYPERTHYROIDISM often associated with ___ ____
how does this occur? (3)
RENAL FAILURE
how does this occur?
1. ELEVATED T4 causes INCREASE in GFR
- when HYPERTHYROID TREATED, causes DECREASED T4 and therefore DECREASED GFR
- because cats usually having CONCURRENT KIDNEY DZ, this can then cause RENAL FAILURE
HYPERTHYROIDISM treatment…
drugs will INHIBIT action of ____ ____, which is used to make…
2 names of drugs?
drugs will INHIBIT action of THYROID PEROXIDASE, which is used to make THYROID HORMONES
2 names?
1. METHIMAZOLE (TAPAZOLE)
- FELIMAZOLE
METHIMAZOLE…
used to treat WHAT?
ADVANTAGES? (2)
DISADVANTAGES? (1)
SIDE EFFECTS usually seen… and are usually ___, as well as…
1.
2.
TREATS HYPERTHYROIDISM
ADVANTAGES?
1. AVAILABLE & INEXPENSIVE
2. can control AMOUNT of THYROID HORMONE PRODUCED, especially important if there’s SUSPECTED RENAL DZ
DISADVANTAGES?
1. owners have to PILL ANIMAL MANUALLY BID
SIDE EFFECTS usually seen within FIRST 3 MONTHS, and are usually GI, as well as…
1. HEPATIC TOXICITY
2. IMMUNE-MEDIATED
3 ROUTES of ADMINISTRATION for METHIMAZOLE?
how long/often should we MONITOR for SIDE EFFECTS & if we need to CHANGE DOSE?
- PO
- LIQUID
- TRANSDERMAL
should monitor EVERY 2-3 WEEKS for FIRST 3 MONTHS for SIDE EFFECTS & DOSAGE
when is THYROID SURGERY indicated? (2)
advantages? (3)
disadvantages? (3)
indications?
1. only if there’s a BIG/CYSTIC THYROID MASS
2. if we need to REMOVE WHOLE THYROID
advantages?
1. can be CURATIVE
2. NO LIFELONG MEDS
3. NO MONITORING BLOOD LEVELS
disadvantages?
1. COST
2. requires GA
3. can cause HYPOCALCEMIA because PARATHYROID CAN BE COMPROMISED
I-131 treatment…
= what is it?
advantage? (1)
disadvantages? (2)
= RADIOACTIVE TREATMENT with RADIOACTIVE ISOTOPE OF IODINE that will be MORE READILY TAKEN UP BY NEOPLASTIC THYROID CELLS
advantages?
1. 1 SQ injection can be CURATIVE
disadvantages?
1. need to be AUTHORIZED to work with RADIOACTIVE MATERIALS, so animal needs to be HOSPITALIZED BY LAW ($$$)
2. animals can become HYPOTHYROID
animals treated with I-131 for HYP__THYROIDISM lived ___ than when treated with METHIMAZOLE
HYPERTHYROIDISM, LONGER
if a cat has HYPERTHYROIDISM but VARIABLE KIDNEY FUNCTION, then you should likely do a…
TRIAL for METHIMAZOLE
CANINE HYPERTHYROIDISM…
commonality?
can be caused by… & MOST animals have ____ ___ at the time of presentation
often has ___ to ____ prognosis
RARE in dogs
can be caused by THYROID CARCINOMAS that are LARGE & INVASIVE; & MOST animals have CERVICAL MASSES at the time of PRESENTATION
often has POOR to GRAVE prognosis
what is the MOST COMMONLY DIAGNOSED ENDOCRINOPATHY in the…
DOG?
CAT? in WHAT AGES?
DOG = CANINE HYPOTHYROIDISM
CAT = FELINE HYPERTHYROIDISM if MIDDLE to OLDER AGE
CANINE HYPOTHYROIDISM…
commonality?
has HIGH incidence of ___ DIAGNOSIS
most COMMON cause is ___-mediated ___ of the THYROID GLAND
biopsy?
in NECROPSY, can sometimes see…
COMMON disease
HIGH incidence of FALSE DIAGNOSIS
usually IMMUNE-mediated DESTRUCTION of the THYROID GLAND
biopsy is NOT HELPFUL because IT WILL NOT TELL US FUNCTION
in NECROPSY, can sometimes see SEVERE THYROID ATROPHY (almost no thyroid left)
2 NEOPLASMS that can cause CANINE HYPOTHYROIDISM?
often cause ____ ____ of the thyroid gland
but this is an ____ cause
2 NEOPLASMS..
1. CARCINOMA
2. SQUAMOUS CELL CARCINOMA
often cause NEOPLASTIC DESTRUCTION
UNCOMMON cause
what DRUG can cause CANINE HYPOTHYROIDISM?
TMS
CANINE HYPOTHYROIDISM..
occurs in WHAT aged dogs? & give specific range
tends to affect WHAT size dogs? give 2 breeds
intact/fixed dogs & sexes likely? (2)
occurs in MIDDLE-AGED dogs 4-10 YEARS
tends to affect MID-LARGE breed dogs…
1. GOLDEN RETRIEVERS
2. DOBERMAN PINSCHERS
SPAYED FEMALES & NEUTERED MALES LIKELY
CANINE HYPOTHYROIDISM…
clinical signs tend to be ___
common UNIQUE clinical signs? (5) which finding is MOST COMMON?
can also see many ____ & ____ signs!
SOMETIMES, can see ____ signs!
clinical signs tend to be PROGRESSIVE
common UNIQUE clinical signs?
1. EXERCISE INTOLERANT
2. CONSTIPATION –> MOST COMMON
3. MENTAL DULLNESS
4. ANOREXIA
5. HEAT-SEEKING
can also see many DERMATOLOGIC & NEUROMUSCULAR signs!
SOMETIMES, can see REPRODUCTIVE signs!
DERMATOLOGIC signs in CANINE HYPERTHYROIDISM? (4)
- DULL, DRY FLAKEY COAT
- SECONDARY PYODERMA
- SEBORRHEA
- SYMMETRIC ALOPECIA
in INTACT FEMALES with HYPOTHYROIDISM, causes WHAT 2 signs?
- affects FERTILITY
- DECREASES LIBIDO
CONGENITAL HYPOTHYROIDISM commonality?
RARE
2 CARDIOVASCULAR signs in HYPOTHYROIDISM?
- BRADYCARDIA
- CARDIAC ARRHYTHMIAS
MYXEDEMA COMA…
can be a sign associated with WHAT DZ?
commonality?
animals often present…
can be associated with HYPOTHYROIDISM
EXTREMELY RARE
animals often present COMATOSE/NEUROLOGICAL
WHY is CANINE HYPOTHYROIDISM often OVER-DIAGNOSED?
what SHOULD be done?
people usually ONLY TEST TOTAL T4 and use that as DIAGNOSIS!
INSTEAD, should combine LOW TOTAL T4 with HIGH TSH
ONE COMMON CBC finding in HYPOTHYROIDISM?
which value should we take MULTIPLE measurements of? why?
- HYPOCHOLESTEROLEMIA
take MULTIPLE measurements of TOTAL T4 because LOW T4 CAN BE PRESENT FOR MANY REASONS
if you have to choose ONE thyroid test for HYPOTHYROIDISM, choose ___ ___ because it’s….
FREE T4 because it’s LESS AFFECTED BY NON-THYROIDAL DISEASE
TSH test…
can be used to test for ____
if POSITIVE for that disease, expect HIGH/LOW TSH
BEST DIAGNOSIS for this when COMBINED with WHAT test & WHAT result for this disease?
TESTS FOR HYPOTHYROIDISM
if HYPOTHYROID –> TSH IS HIGH, A LOT OF SUPPRESSION
BEST HYPOTHYROIDISM DIAGNOSIS when COMBINED with TOTAL T4 BEING LOW
what is the GOLD STANDARD for HYPOTHYROIDISM?
TSH-STIM TEST
