Unit 2: Hormones That Affect Growth And Metabolism Flashcards
Hormones that affect growth and metabolism:
1. Human growth hormone (hGH):
•secreted by the anterior pituitary.
•increases protein synthesis, cell division and growth (of bone and muscle tissue in particular), and metabolic release of stored fats.
•especially important during puberty:
-hyposecretion: pituitary dwarfism.
-hypersecretion (adulthood): acromegaly.
-hypersecretion (childhood): gigantism.
Growth hormone disorders (gigantism):
•overproduction of GH in childhood caused an increase in growth of bones, muscles and organs.
-becomes extremely tall (possibly 8-9 feet) but body proportions are normal.
Growth hormone disorders (acromegaly):
•overproduction of GH in an adult leads to the growth of some bones like eyebrow ridge, lower jaw, nose, hands, feet.
Growth hormone disorders (dwarfism):
•short stature resulting from a decreased production of GH leading to delayed sexual development and skeletal development.
•low muscle tone, is common in dwarfs, but intelligence and lifespan are usually normal.
Hormones that affect growth and metabolism:
2. Thyroxine:
•secreted by the thyroid gland after stimulation by topic hormone TSH (released from anterior pituitary).
•increases the rate at which the body metabolizes fats, proteins, and carbs.
•targets many organs.
-hyperthyroidism: Grave’s disease (immune system attacks thyroid).
-hypothyroidism: tired, weight gain.
The hypothalamus and anterior pituitary control the secretion of thyroid hormones through:
-two negative feedback loops.
1. Hypothalamus releases thyroid releasing hormone (TRH) to the anterior pituitary.
2. Anterior pituitary releases thyroid stimulating hormone (TSH) to the thyroid gland.
3. Thyroid gland produces thyroxine which feedback to the anterior pituitary to stop releases TSH.
4. Production of thyroxine also feedback to the hypothalamus to stop producing TRH.
TSH:
-thyroid stimulating hormone.
Disorders of the thyroid gland (1.hypothyroidism):
-the thyroid gland does not make enough thyroid hormone.
•causes: inflammation of the thyroid gland, which damages the gland’s cells or autoimmune disease in which the immune system attacks the thyroid gland.
•symptoms: cold, fatigue, dry skin, hair loss, weight gain, sleep a lot, goiter.
•cretinism: hypothyroidism in children—> leads to abnormal mental and physical development, growth ret…
Disorders of the thyroid gland (2.hyperthyroidism):
-the thyroid gland makes too much thyroid hormone.
•the condition is often referred to as an “overactive thyroid”.
•causes: getting too much iodine, Grave’s disease (autoimmune disease), inflammation (thyroiditis) of the thyroid due to viral infection, non-cancerous growths of the thyroid gland or pituitary gland.
•symptoms: increased metabolism, difficulty concentrating, heat intolerance, increased appetite, increasing sweating, nervousness, restlessness, weight loss, goiter.
•treated by removing a portion of the thyroid gland.
Thyroxine and iodine:
•the thyroid requires iodine to produce thyroxine.
•insufficient iodine in the diet thus inhibits thyroxine production, meaning there will be no signal to stop the secretion of TSH.
•the constant stimulation of the thyroid gland by TSH that results leads to the development of a goitre.
Disorders of the thyroid gland
(3. Goiter):
•enlargement of the thyroid gland.
•may be due to iodine deficiency or overactive thyroid.
•iodine is required to synthesize thyroxine.
•without iodine, thyroid production and secretion of thyroxine drops.
•this causes more and more TSH to be produced, and the thyroid is stimulated more and more.
•under relentless influence of TSH, cells of the thyroid continue to develop and the thyroid enlarges.
•this occurs in regions of the world where the diet lacks iodine.
•in many countries, iodine is added to salt to prevent this condition.
Thyroxin production is controlled by:
-negative feedback.
Hormones that affect growth and metabolism:
3. Calcitonin:
•secreted by the thyroid.
•plays a role in the regulation of blood calcium levels.
•high concentrations of calcium in the blood trigger the release of calcitonin, which stimulates the uptake of calcium into bones (thus lowering blood calcium levels).
-HINT: calcitonin in the bonin…
Hormones that affect growth and metabolism:
4. Parathyroid hormone (PTH):
•secreted by the parathyroid.
•plays a role in the regulation of blood calcium levels.
•low concentrations of calcium in the blood trigger the release of PTH, which stimulates bone cells to reabsorb calcium into the blood (thus raising blood calcium levels).
-calcitonin and PTH are said to work antagonistically (in opposition).
TRH:
-thyroid releasing hormone.
