TH Pathophysiology Flashcards
What are the three mechanisms that can result in thyroid hormone dysfunction?
- Alterations in the circulating levels of TH
- Impaired metabolism of TH in the periphery
- Resistance to TH actions at the tissue level
Define euthyroid state.
An individual whose thyroid function is normal
What is primary hypothyroidism?
Insufficient synthesis of TH due to lack of iodine in the diet
What are the consequences of fetal hypothyroidism during early development?
Cretinism in humans, resulting in decreased mental capacity
What are common symptoms of hypothyroidism in adults?
- Goiter
- Lack of appetite
- Slow heart rate
- Dermatological disorders
- Reduced fertility
What indicates iodine deficiency in a herd?
Goiter of newborn animals
What causes secondary hypothyroidism?
Pituitary lesions on thyrotropes resulting in decreased TSH release
What is tertiary hypothyroidism?
Hypothalamic failure leading to decreased TSH and T4 release
What is Autoimmune Thyroiditis?
A common cause of hypothyroidism where the immune system attacks normal follicles
What is Hashimoto’s Disease?
An autoimmune condition leading to hypothyroidism, especially common in females aged 30-50
What lab values are indicative of hypothyroidism?
- High TSH
- Low T4
- Detection of TPOAb
- Detection of TGBAb
List some symptoms of hypothyroidism in animals.
- Decreased metabolic rate
- Cold-intolerant
- Lethargy
- Obesity
- Brittle nails
- Thinning hair
- Dry skin
- Bradycardia
What is the primary treatment for hypothyroidism?
Administration of synthetic T4, such as Synthroid
What is hyperthyroidism?
A condition caused by autoimmune disease leading to increased production and release of thyroid hormones
What are the symptoms of hyperthyroidism?
- Increased metabolic rate
- Warm-intolerant
- Weight loss
- Nervousness
- Rapid heart rate
- Exophthalmos
What are the diagnostic markers for hyperthyroidism?
- Low TSH
- Normal/high Free-T4
- Anti-TSH Ab
What is the most common cause of hyperthyroidism in cats?
Thyroid adenoma
What are the treatment options for hyperthyroidism?
- Surgical ablation (thyroidectomy)
- Radioactive iodine treatment
- Administration of antithyroid drugs
What is the mechanism of action for thioamide drugs?
Inhibit iodination of tyrosines and coupling of MIT and DIT to form T3 and T4
Define metamorphosis in the context of amphibians.
Change in form or transformation, most pronounced in amphibians
What are the effects of thyroid hormones during metamorphosis?
- Cell proliferation and differentiation in limbs
- Functional differentiation in liver and lungs
- Complete regression of the tail
- Restructuring of the brain
How does thyroid hormone play a role in bird hatching?
It influences the transition from a protected environment inside the egg to a hazardous terrestrial life
What characterizes the peri-hatch period in precocial birds?
Peak values of blood thyroid hormones
What happens to hatching when circulating TH levels are prevented from rising in precocial birds?
Hatching is delayed or inhibited
