Dermatology and Endocrine Diseases Flashcards
What are your dermatologic differential diagnoses?
- Parasitic: fleas, scabies, demodex, other
- Allergic: environ, food, parasite, contact
- Immune mediated/Idiopathic
- Neoplastic
- 4: 1-4 other misc (refer to someone else)
- Microbial: bacteria, yeast, dermatophyte
- Endocrine: endogenous
What are 3 endocrine dermatopathies?
- hypothyroidism (dogs)
- Cushing’s dz (dogs, cats, horses)
- Alopecia X (dogs)
What are general concepts regarding endocrine dermatopathies?
- usually middle aged animals
- alteration in hair coat (alopecia, texture)
- underlying non-pruritic dz, responsible for recurrent skin and ear infections
What is the different between T3 and T4?
- T3 = more metabolically active
- mainly intracellular
- only 10-20% produced directly by thyroid, most from deiodination of T4
- T4 = most often on measured clinically
- main thyroid secretory product that is tested, but not as biologically active
What are the functions of thyroid hormones?
- growth
- protein synthesis
- lipid metabolism
- carb metabolism
- hematopoiesis
- reproduction
What occurs if a patient has low thyroid hormone?
- Growth: alopecia
- Protein synthesis: altered metabolism
- Lipid metabolism: elevated cholesterol
- Carb metabolism: alteration
- Hematopoiesis: anemia (mild)
- Reproduction: decreased
What are the general (non-derm) clinical signs of hypothyroidism?
- Metabolic: lethargy ,inactivity, wt gain, cold intolerance
- Reproductive: persistent anestrus, testicular atrophy
- CV: bradycardia, cardiac arrhythmias
- GI: diarrhea, constipation
- Hematologic: anemia, hyperlipidemia
- Neuromuscular: seizures, ataxia, circling, vestibular signs, facial n. paralysis
- Ocular: corneal lipid deposits, uveitis
What are the dermatologic clinical signs of hypothyroidism?
- seborrhea: dry or greasy
- skin and/or ears
- may not be affected
- recurrent infections: skin and/or ears
- hyperpigmentation
- dry, brittle hair coat
- alopecia: variable
- different patients, different constellations of symptoms
What are the breed predilections for hypothyroidism?
- Golden retrievers
- Dobies
- Dachshund
- Great Dane
- Poodle
- Boxer
How do you diagnose hypothyroidism?
- CBC: normochromic, normocytic, non-regenerative anemia
- Chem: incr cholesterol and triglycerides
- Thyroid panel:
- decr TT4, FT4 = decr T4 (most common)
- TSH (incr primary hypothyroidism, but decr in secondary and tertiary hypothyroidism)
- TT3 and FT3 unreliable
What are some factors that affect thyroid hormone synthesis?
- age
- breed
- drugs
- illness (euthyroid syndrome)
- hypoproteinemia
- obesity
What are the advantages of FT4 over TT4?
- direct correlation w/ availability to tissues, rate of metabolism and excretion
- less influenced by medical conditions and drug competition
- most labs offer “inexpensive” T4
What changes on a skin biopsy might be suggestive of endocrine disease?
- hyperkeratosis and follicular keratosis
- incr in telogen hair follicles
How do you treat hypothyroidism?
- synthetic T4 supplementation (L-thyroxine)
- monitor: post pill check 6 hrs after dose, 6 wks after beginning treatment
What are some reasons for therapeutic failure for hypothyroidism?
- wrong diagnosis, dose, product, frequency
- irregular admin
- failure to ingest the medication
- poor absorption from the gut
- rapid metabolism/excretion
- auto-antibodies to T3 or T4
- target organ resistance
