Endocrine (Gram) Flashcards
Dermatologic differential diagnosis: PAIN 4 ME
- Parasitic (fleas, scabies, demodex)
- Allergic (environment, food, parasite, contact(
- Immune mediated/Idiopathic/Idunno
- 4 - other misc.
- Microbial (bacteria, yeast, dermatophyte)
- Endocrine (endogenous)
General concepts of endocrine disease
- Middle aged animals
- Alteration in hair coat (alopecia, texture)
- Underlying non-pruritic dz responsible for recurrent skin and ear infections (which can itch)
Primary hypothyroidism
Thyroid
- Idiopathic atrophy
- lymphocytic thyroiditis
- neoplasia
Secondary hypothyroidism
Pituitary gland
Tertiary hypothyroidism
Hypothalamus
Sick euthyroid
Hypothyroidism induced by medications or just being sick
T4
- most often measured clinically (important for testing)
- made directly from the thyroid in higher amounts than T3
- not as biologically active as T3
T3
- more metabolically active than T4
- mainly intracellular
- 10-20% produced directly from thyroid
- 80-90% derived from T4
Thyroid physiology
- Turnover rate is higher in dogs than humans
- replacement dose needs to be much higher
- Thyroid hormones bind to proteins
Functions of thyroid hormone
- Growth
- Protein synthesis
- Lipid metabolism
- Carb metabolism
- Hematopoiesis
- Reproduction
Low thyroid effect on growth
Alopecia
Low thyroid effect on protein metabolism
Altered metabolism
Low thyroid effect on lipid metabolism
Elevated cholesterol
Low thyroid effect on hematopoiesis
Mild anemia
Low thyroid effect on reproduciton
Decreased
Dermatologic signs of hypothyroid
- Seborrhea - dry & greasy
- Recurrent infections
- Hyperpigmentation
- Dry, brittle hair coat
- Alopecia
Breed predilection for hypothyroidism
- Golden retrievers
- Doberman pinschers
- Dachshunds
- Great danes
- Poodles
- Boxers
Diagnosis of hypothyroid
- CBC (normocytic, normochromic, non-regenerative anemia)
- Chem (incr. cholesterol & triglycerides)
- Thyroid panel
Thyroid panel w/ hypothyroidism
- Low TT4, FT4
- TSH (high w/ 1º, low w/ 2º & 3º
- TT3, FT3 unreliable
Factors affecting thyroid hormone concentrations
- Age
- Breed
- Drugs
- Illness (euthyroid)
- Hypoproteinemia
- Obesity
Advantages of FT4 to TT4
- Direct correlation w/ availability to tissues, rate of metabolism, and excretion
- Less influenced by medical conditions and drug competition
Skin Biopsy
- Helpful but rarely diagnostic
- Hyperkeratosis, follicular keratosis, incr. in telogen hair follicles suggests endocrine dz
Hypothyroid treatment
- Synthetic T4 supplementation
- L-thyroxine
- Solixine
Reasons for therapeutic failure (hypothyroidism)
- Wrong diagnosis, dose, product, frequency
- Irregular admin
- Failure to ingest meds
- Poor absorption from the gut
- Rapid metabolism/excretion
- Auto-antibodies to T3, T4
- Target organ resistance
Types of hyperadrenocorticism (Cushing’s)
- Iatrogenic (exogenous glucocorticoids)
- Endogenous (adrenal, pituitary*)
*most common
Dermatological signs of Cushing’s
- Comedones (+/- demodex)
- Recurrent infections
- Demodicosis (mange)
- Cutaneous atrophy
- Hyperpigmentation
- Calcinosis cutis
Cushing’s tests
- ACTH stim
- Low dose dexamethasone suppression test
- Serum ACTH concentrations
- High dose dex suppression test
Cushing’s in cats
- Diabetes mellitus
- Skin fragility
Alopecia X - alternative names
- Growth hormone responsive dermatosis
- Adrenal sex hormone imbalance
- PseudoCushings
- Castration responsive dermatosis
Alopeica X clinical signs
- Bilaterally symmetrical alopecia
- Head & extremities are spared
- Hyperpigmentation
- No systemic abnormalities
Alopecia X diagnosis
R/O hypothyroidism and Cushing’s
Alopecia X treatment
- Not necessary
- Melatonin
- Castration recommended
- Methyltestosterone (neutered)
- Ketoconazole
- Lysodren
- Trilostain
Sertoli cell tumor dermatologic signs
- Resolve w/ castration
- Bilateral, symmetrical alopecia
- Hyperpigmentation
- Seborrhea
- Ceruminous otitis externa
- Gynecomastia
- Linear preputial dermatosis
