LECTURE 37: thyroid hormones Flashcards
List the general physiological effects of thyroid hormones
growth & development
metabolic effects
thermogenesis
CV effects
Describe the “growth & development” effects of thyroid hormones
Essential for brain development
- Absent T-3 → cretinism
Promote protein synthesis (skeletal/muscle growth)
- Anabolic at normal concentrations
- Catabolic at the levels of hyperthyroidism
Describe the metabolic effects of thyroid hormones
- Increase basal metabolic rate (BMR)
- Increase oxygen consumption
- Starvation lowers both T-3 hormone and thyroid receptor
Describe the “thermogenesis” effects of thyroid hormones
Increase resting heat production
- Inability to adjust to environmental temperature is a characteristic symptom of hyper- or hypothyroidism
CV effects
Describe the CV effects of thyroid hormones
Increased catecholamine sensitivity (increased HR)
Define HYPOthyroidism
Deficiency of thyroid hormones
Define HYPERthyroidism
Excessive levels of thyroid hormones (thyrotoxicosis)
List the symptoms of HYPOthyroidism
- Decrease in metabolic rate →
fatigue, mental dullness, lethargy, inattention - Defective thermoregulation
- May occur with thyroid enlargement
(nontoxic goiter) - Dwarfism and mental retardation (cretinism) in infants and children
- Myxoedema coma →
end state of untreated hypothyroidism;
water intoxication, shock, and death
List the symptoms of HYPERthyroidism
- Excessive metabolism →
poor thermoregulation and weight loss - Increased heart rate and cardiac output
List the causes of HYPOthyrodism
Hashimoto’s thyroiditis → most common; autoimmune disease that destroys the thyroid gland
- Destruction or removal of the gland
(radiation, X-ray, thyroidectomy) - Iodine deficiency
- Congenital (cretinism)
- Secondary → TSH deficiency
List the causes of HYPERthyrodism
Graves’ disease → Most common; autoimmune; thyroid-stimulating IgG;
enlargement of the entire thyroid gland (diffuse toxic goiter)
- Toxic uninodular goiter and toxic multinodular goiter → Adenoma producing excess T-3; occur mostly in older women
- Subacute thyroiditis → Viral infection of the thyroid gland; transient release of stored thyroid hormones
Describe the skin effects of HYPOthyroidism
Pale, cool, puffy
Describe the eye effects of HYPOthyroidism
Drooping of eyelids
Describe the CV effects of HYPOthyroidism
Bradycardia
Decreased cardiac output
Increased vascular resistance
Describe the CNS effects of HYPOthyroidism
Lethargy
Describe the metabolic effects of HYPOthyroidism
Decreased appetite
Decreased BMR
Hypoglycemia
Increased cholesterol and
triglycerides
Decreased drug metabolism
Describe the CV effects of HYPERthyroidism
Tachycardia
Increased cardiac output
Decreased vascular resistance
Describe the CNS effects of HYPERthyroidism
Nervousness
Describe the metabolic effects of HYPERthyroidism
- Increased appetite
- Increased BMR
- Hyperglycemia
- Decreased cholesterol and
triglycerides - Increased drug metabolism
Define goiter
an enlargement of the thyroid gland due to a persistent rise in TSH
Describe the difference between a toxic and nontoxic goiter
no excess hormone is produced due to a nontoxic goiter
a toxic goiter produces excess hormone (T3)
Describe the pathology of Hashimoto’s thyroiditis
- Can cause hypothyroidism
- Autoimmune disease that destroys the thyroid gland
Describe the pathology of Grave’s disease
- Can cause hyperthyroidism
- Autoimmune
- Thyroid-stimulating IgG
- Enlargement of the entire thyroid gland (diffuse toxic goiter)
List the drugs used for thyroid hormone replacement therapy
Levothyroxine (Synthroid®, Levoxyl®)
Liothyronine (Cytomel®)
List treatment options for hyperthyroidism
Thioamides → inhibits thyroid peroxidases
- Methimazole (Northyx®,Tapazole®)
- Propylthiouracil (Propycil®)
Iodide → larges doses inhibits its own uptake
- Lugol’s solution → aq solution of elemental I and KI
- KI
