Weight gain and hypothyroidism Flashcards
Increased adipose tissue not the only possible cause of increased body mass, what are the non-pathological and pathological causes of increased lean mass?
Non pathological increased
* lean mass
* Exercise,
* Growth
* Pregnancy
Pathological increased lean mass
* Neoplasia
* Hyperplasia
* Inflammation
* Cysts/abscesses
* Organomegaly- disease/ iatrogenic (e.g. Cushing’s / GCs)
* Fluid retention
* Hypervolaemia
* Oedema
* Third spacing (Ascites, Pleural effusion, Pericardial effusion)
Don’t rely on weight.
Body Condition Score your patients as part of every clinical exam
what are the three categories that can cause weight gain?
Non pathological
* Over feeding
* Reduced exercise (possible pathology)
* Predispositions - Age, Neutering, Breed, Owner
Increased appetite
* Systemic disease normal caloric demand- e.g. Hyperadrenocorticism
* Systemic disease - higher caloric demand - Acromegaly, Insulinoma
* Iatrogenic- e.g. glucocorticoids, phenobarbitone, mirtazapine
* Behavioural/ psychological/ neurological
Normal appetite but decreased metabolic rate
* Hypothyroidism
What is Acromegaly?
what is the difference in the cause in dogs and cats?
what care the clinical signs?
Increased growth hormone
* Cats - usually associated with functionalpituitary adenoma
- mostly males middle age/older
* Dogs - usually unneutered females
* due to elevated progesterone levels in the luteal phase OR exogenous progesterone admin (iatrogenic)
Clinical signs
* Increased risk Diabetes Meletus due to insulin resistance - polyuria,polydipsia, andpolyphagia. BUT weight gain instead of weight loss.
* Cutaneous thickening,macroglossia (big tounge), increased dental spacing,prognathism
how is acromegaly diagnosed and what are the treatment options?
Diagnosis
Clinical signs + elevated serum GH and IGF-1 (early insulin therapy can cause false –ives)
Treatment options
* Surgery- Tx of choice
- Dogs OVH and mammary strip
- Cats Hypophysectomy but £££ and invasive
* radiotherapy,
* drugs such e.g. somatostatin analogues, dopaminergic agonists (e.g. cabergoline) and GH receptor antagonists
how are insulinomas diagnosed?
Bloods
* Demonstrate hypoglycaemia (BG < 3mmol/l) while clinical signs, which resolve with glucose admin
* History clinical exam and routine bloods
* exclude other causes of hypoglycaemia (e.g. sepsis, liver failure, Addison’s, toxin ingestion etc)
* Increased suspicion if
* Increased insulin:glucose (not sens or spec)
* Low fructosmaine
imaging
* Ultrasound and x-ray chest and abdomen
* looking for mass or mets
* 50-75% insulinomas visible on ultrasound
* Dual-phase CT angiography may be the best but still can miss some
For small lesions ex-lap may be required for diagnosis and treatment
what is the three treatment options for insulinomas?
Treatment - surgery
* Excisional biopsy treatment of choice
* Even with mets can reduce clinical signs
* Care to correct BG before/during GA
* Nodulectomy or partial pancreatectomy
* Possible post op complications
* pancreatitis, persistent hypoglycaemia (incomplete removal/mets) DM, hyperglycaemia (beta cell atrophy)
Medical management
If surgery not feasible/ recurrence/ persistent hypoglycaemia
* Diet- multiple small meals high in protein, fat, and complex carbs
* Prednisolone- 0.25mg/kg BID- insulin antagonist and stimulates gluconeogenesis and glycogenolysis.
* Octreotide- inhibits insulin synthesis and secretion.
* Diazoxide- 5-10 mg/kg BID- stimulates gluconeogenesis and glycogenolysis decreases insulin release
Chemotherapy
Streptozotocin-adjunctive chemo agent- cytotoxic to pancreatic βeta cells. Caution as nephrotoxic and can cause DM
how are thyroid hormones produced?
what are the actions of the thyroid hormones?
T3/T4 actions
* Increase basal metabolic rate,
* Affectprotein synthesis
* Regulate long bone growth and neural maturation
* Increase the body’s sensitivity tocatecholamines
* Regulateprotein,fat ,andcarb metabolism,
* Stimulate to heat generation
* Stimulate vitamin metabolism
what is hypothyroidism?
what is the difference between dogs and cats?
what are the causes?
Insufficient production of T3 (triiodothyronine) and T4 (thyroxine) by thyroid gland.
Common in dogs, rare in cats (except iatrogenic)
Causes:
Primary (>95% of cases in dogs)
- Idiopathic thyroid gland atrophy OR
Immune-mediated lymphocytic thyroiditis
Secondary
* Space occupying mass in pituitary destroying pituitary thyrotrophs
Congenital
- Abnormal thyroid gland development OR
- Dyshormonogenesis of thyroid hormone, OR
- Abnormal thyroid-stimulating hormone (TSH) production
Iatrogenic (cats)
- Usually following excessive treatment for hyperthyroidism
what is the signalment of hypothyroidism in dogs and cats?
what are the clinical signs?
Dogs
* Middle age- older
* Mostly large breed (Including Golden Retrievers, Doberman, Dachshund, Cocker Spaniel…)
* Increased risk if female neutered?
Cats
* Usually older cats following treatment for HyperT4
* Often little/ no signs but can worsen renal dx (reduced BP and GFR) so need to monitor for this and if occurs treat.
* Reduce meds or supplement thyroxine as dogs
Clinical signs:
Very variable! Easy to attribute to normal aging
* Demeanour- dull, lethargic, exercise intolerant
* BCS- weight gain without increased appetite, obesity
* Temp- hypothermia, heat seeking behaviour.
* Skin/coat- Dry, +++ shedding, slow hair regrowth. Symmetrical alopecia of trunk/thighs/tail/ neck, hyperpigmentation. Occasionally, secondary pyoderma and pruritis
* Tragic facial expression (myxoedema- increased GAGs in skin make facial folds more pronounced)
* Neuro- increased risk of peripheral neuropathies/ megaoesophagus, vestibular dx etc, myxoedema coma (rare!) (Signs associated with tumour possible if 2ndary)
* CVS- hypotension, bradycardia
* Repro issues/failure
what are the clinical sings congenital hypothyroidism?
- Disproportionate dwarfism
- Dullness, lethargy and impaired mental development
- Goitre (enlarged thyroid gland)
- Epiphyseal dysgenesis (underdeveloped growth plates in long bones), short vertebral bodies, and delayed growth plate closure.
- Retained puppy coat
- Poor appetite
- Constipation
- Delayed dental eruption.
- Neuromuscular signsincluding tremors, proprioceptive deficits, exaggerated spinal reflexes
Diagnosis and treatment as for adult form
how is hypothyroidism diagnosed?
what is euthroid sick syndrome?
what is the effect of glucocorticoids, sulphonamides and phenobarbitone on TT4, FT4 and TSH levels?
Routine bloods-
* Haematology- normocytic, normochromic, nonregenerative anaemia (50%)
* Biochemistry- hypercholesterolemia (80%) triglycerides, alkaline phosphatase, and CK.
Definitive diagnosis
Compatible signs + LOW Total T4/ Free T4 and NORMAL-HIGH TSH
- If equivocal further testing possible (scintigraphy, TSH stim) but not widely available.
- If still unsure consider treatment trial - not ideal
Lots of nonthyroidal illness and certain drugs can lead to low serum thyroid hormone measurements in dogs and cats which do NOT have thyroid disease. - euthyroid sick syndrome.
Many of these conditions have signs similar to hypothyroidism and some of the clinical signs can even improve after levothyroxine administration despite not being truly hypothyroid!
These cases will usually have ** LOW Total T4/ Free T4 and LOW/NORMAL TSH**
Which test(s) would you chose to confirm a diagnosis of hypothyroidism in a dog with compatible clinical signs?
Total T4/ Free T4 and TSH
what is the treatment and monitoring of hypothyroidism?
Treatment
Levothyroxine - 0.02-0.04mg/kg SID or divided BID
- With or without food- be consistent
- Lifelong treatment
Monitoring
* Monitor for signs of clinical improvement
* Repeat Total T4 and adjust treatment as needed
* Ideal trough value just before dosing > 19 nmol/l
* Ideal peak value 3 hrs post pill 30-47 nmol/l
* Once stable monitor every 6-12 months
how are insulinomas stages and what is the prognosis?
Staging
Stage I: Only pancreas affected
Stage II: Regional lymph node metastasis
Stage III: Distant metastasis
Median survival
Stage I- with surgical excision >2 years
Stage II or III- approx. 6 months regardless of treatment.
what are Insulinomas?
what are the presispositions?
what are the clinical signs?
- Functional neuroendocrine tumour of pancreas
- beta cells of islets of Langerhans
- Secretes multiple hormones including somatostatin, glucagon, gastrin, pancreatic polypeptide, IGF1 and serotonin and INSULIN.
- Excessive insulin –> Low BG –> clinical signs
- Uncommon in dogs, rare in cats
- Any gender, more common in large breeds
- Mostly malignant
Clinical signs
* Increased appetite and weight gain (BCS)
* Weakness, ataxia, collapse, seizures
* Particularly after exercise/ fasting OR feeding (stimulates insulin release)
* Glucose admin improves signs
