Weight gain and hypothyroidism

• Functions of adipose tissue

  Remember that adipose tissue is a multifunctional organ and should be treated that way and kept in top condition.

  • Regulates inflammatory responses.
  • Regulated energy usage and storage.
  • Regulates hunger responses.
• Life stage diets and adult maintenance

  Maintenance is the amount if energy required to achieve everything required in their daily life with minimal left over. Life stage is what age our animal is and how this may affect their daily energy needs. Senior require less if no longer breeding. Adult requires more to satisfy activity, puppy for growth.
• Unhealthy weight gain

  Obesity is a medical condition but we need out fat cells to produce energy when our normal stores run low. Obesity is classed as an individual that exceeds it expected or optimal body weight by 20%. Water/fluid has weight therefore a patient with retained fluid will consequently weigh more.
• Problems associated with an unhealthy weight increase

  Arthritis

  Diabetes

  Heart disease

  Skin disease

  Lower urinary tract problems.

  Hepatic lipidosis (liver problems.
• Losing weight in cats

  If weight is lost to quick, it will show as the catabolism of muscle and visceral tissue. Muscle wastage, hepatic lipidosis. Cats will mainly break down protein fir the creation of glucose to be used in cells, if they are restricted in their access to these then they will catabolise their own tissue.

  Cats can use fats as a form of energy, but they take time to break down and if the process happens to quickly, they can get hepatic lipidosis which can seriously affect liver function to other systemic problems.
• What is DER

  Daily energy requirements = exercise routine, neutered status, sex of the animal, pregnancy status, illnesses, existing conditions.
• What is safe weight loss?

  Safe weight loss should be 1% per week in cats,

  Safe weight loss should be 1-2% per week in dogs.

  Target weight could be up to 30% but may need to be adjusted to slow down weight loss.

  An initial target weight may be needed in the middle of current and final target.
• Calculating an ideal weight

  Take the info from the consult and calculate the patients ideal body weight. If you calculate them as a BCS of 6 for example you take their current bodyweight and divide it by 1.1
• Non-pathological causes of weight gain

  Exercise

  Growth

  Pregnancy
• Pathological causes of weight gain

  Neoplasia

  Hyperplasia

  Inflammation

  Cysts/abscesses

  Organomegaly - disease/iatrogenic

  Fluid retention

  • Hypovolaemia
  • Oedema
  • Third spacing
  • Ascites
  • Pleural effusion
  • Pericardial effusion
• Common non-pathological causes of weight gain

  Over-feeding

  Reduced exercise (possible pathology).

  Predispositions

  • Age, neutering, breed, owner.
• Common increased appetite causes of weight gain

  Systemic disease normal caloric demand e.g. Hyperadrenocorticism

  Systemic disease - higher caloric demand, acromegaly, insulinoma.

  Iatrogenic - e.g. glucocorticoids, phenobarbitone, mirtazapine.

  Behavioural/ psychological/ neurological.
• Weight gain due to acromegaly in cats and dogs overview.

  Cats:

  • Usually associated with functional pituitary adenoma.
  • Mostly males middle age/ older.

  Dogs:

  • Usually unnuetered females.
  • Due to elevated progesterone levels in the luteal phase OR exogenous progesterone admin (iatrogenic).
• Weight gain due to acromegaly in cats and dogs - clinical signs

  Increased risk of diabetes Meletus due to insulin resistance - polyuria, polydipsia, and polypahgia. Causes weight gain instead of weight loss.

  Cutaneous thickening, macrogloassia, increased dental spacing, prognathism.
• Weight gain due to acromegaly in cats and dogs diagnosis and treatment.

  Diagnosis:

  • Clinical signs + elevated serum GH and IGF-1 (early insulin therapy can cause false positives).

  Treatment:

  • Surgery is the treatment of choice.
  • Dogs OVH and mammary strip.
  • Cats Hypophysectomy but expensive and invasive.
  • Radiotherapy
  • Drugs e.g. Somatostatin analogues, dopaminergic agonists (e.g. cabergoline) and GH receptor antagonists.
• Weight gain - Insulinomas overview

  Functional neuroendocrine tumour of pancreas

  • B cells of islets of Langerhans.
  • Secretes multiple hormones including somatostatin, glucagon, gastrin, pancreatic polypeptide, IGF1 and serotonin and insulin.
  • Excessive insulin -> low blood glucose -> clinical signs.

  Uncommon in dogs, rare in cats.

  Any gender, more common in large breeds.

  Mostly malignant.
• Weight gain - Insulinomas 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.
• Weight gain - Insulinomas diagnosis with 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)

  Increased suspicion if:

  • Increased insulin: glucose (not sensitive or specific).
  • Low fructosamine.
• Weight gain - Insulinomas diagnosis with 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 can still miss some.

  For small lesions diagnosis ex-lap may be required for diagnosis and treatment.
• Weight gain - Insulinomas treatment - surgery

  Excisional biopsy treatment of choice.

  Even with mets can reduce clinical signs

  • Care to correct blood glucose before/ during GA.
  • Nodulectomy or partial pancreatectomy.
  • Possible post operative complications
  • Pancreatitis, persistent hypoglycaemia (incomplete removal, mets) DM, hyperglycaemia (B cell atrophy).
• Weight gain - Insulinomas treatment - 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 - 5-10mg/kg BID - stimulates gluconeogenesis and glycogenolysis decreases insulin release.

  Chemotherapy:

  Streptozotocin - adjunctive chemo agent - cytotoxic to pancreatic beta cells. Caution as nephrotoxic and cause DM.
• Weight gain - Insulinomas staging and median survival prognosis

  Staging:

  • Stage I: only pancreas affected.
  • Stage II: Regional lymph node metastasis.
  • Stage III: distant metastasis.

  Prognosis:

  • Stage I - with surgical excision >2 years.
  • Stage II or III - approximately 6 months regardless of treatment.
• Thyroid hormone - T3/T4 actions

  Increase basal metabolic rate

  Affect protein synthesis

  Regulate long bone growth and neural maturation.

  Increase the body’s sensitivity to catecholamines.

  Regulate protein, fat and carb metabolism.

  Stimulate to heat generation.

  Stimulate vitamin metabolism.
• Causes of primary hypothyroidism

  >95% of cases in dogs.

  Idiopathic thyroid gland atrophy OR

  Immune-mediated lymphocytic thyroiditis.
• Causes of secondary hypothyroidism

  Space occupying mass in pituitary destroying pituitary thyrotrophs
• Causes of congenital hypothyroidism

  Abnormal thyroid gland development OR

  Dyshormonogenesis of thyroid hormone, OR

  Abnormal thyroid-stimulating hormone (TSH) production.
• Causes of iatrogenic (cats) hypothyroidism

  Usually following. excessive treatment for hyperthyroidism.
• Hypothyroidism - typical adult presentation in dogs

  Middle aged to older.

  Mostly large breed (including Golden Retrievers, Doberman, Dachshund, Cocker Spaniel).

  Increased risk if female neutered? No evidence
• Hypothyroidism - typical adult presentation in cats

  Usually older cats following treatment for hyperT4.

  Often little/ no signs but can worsen renal disease (reduced blood pressure and GFR) so need to monitor for this and if occurs treat.

  Reduce medication or supplement thyroxine as dogs.
• Hypothyroidism - typical adult presentation clinical signs

  Dull, lethargic, exercise intolerant.

  Weight gain without increased appetite, obesity.

  Hypothermia, heat seeking behaviour.

  Dry skin coat, increased shedding, slow hair regrowth. Symmetrical alopecia of trunk/thighs/tail/neck, hyperpigmentation. Occasionally, secondary pyoderma and pruritus.

  Tragic facial expression (myxoedema - increased GAGs in skin make facial folds more pronounced).

  Increased risk of peripheral neuropathies/ megaoesophagus, vestibular disease, myoedema (rare).

  Hypotension and bradycardia
• Congenital hypothyroidism - clinical signs

  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 signs including tremors, proprioceptive deficits, exaggerated spinal reflexes.
• Diagnosis of hypothyroidism

  Routine bloods -

  • Haemotology - normocytic, normochromic, non-regenerative anaemia (50%).
  • Biochemistry - hypercholesterolemia (80%) triglycerides, alkaline phosphatase, and CK.

  Definitive diagnosis:

  • Compatible signs + low total T4/ Free T4 and normal=high TSH.
• Treatment of hypothyroidism

  Levothyroxine:

  • 0.02-0.04mg/kg SID or divided BID
  • With or without food - be consistent either way.
  • Lifelong treatment.
• Monitoring of hypothyroidism

  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 hours post pill 30-47 nmol/l.

  Once stable monitor every 6-12 months.