Lab 9 - thyroid hormone, cortisol, growth hormone

what is the functional unit of the thyroid gland?

follicles

what hormones are thyroid hormones like?

steroid-like amine hormones

• but they can be stored

how can thyroid hormones be stored if they are hydrophobic?

use thyroglobulin, a protein that cannot pass across membranes and is stored in colloid

thyroid hormone binds to receptors __ of the target cell

inside —> hydrophobic

follicles trap __ for the synthesis of thyroid hormone

Iodide

steps of synthesis, storage, and secretion of thyroid hormone

1) TSH binding and iodine transport into colloid

2) TG synthesis and exocytosis into colloid

3) T3 & T4 synthesis

4) TG + T3 + T4 synthesis

thyroid hormone cascade

3 hormones:

• TRH

• TSH

• thyroid hormone (T3 & T4)

actions of thyroid hormone (4)

1. metabolic actions - basal metabolic rate (body temp)

2. permissive actions - increases beta-adrenergic receptor (catecholamine expression)

3. growth and development - TH is needed for production of growth hormone

4. growth and development - essential for fetal and adult NS function/development

hypothyroidism

conditions characterized by plasma concentration of thyroid hormone that are chronically below normal

hyperthyroidism

conditions characterized by plasma concentration of thyroid hormone that are chronically above normal

causes & symptoms of hypothyroidism

causes: iodine deficiency, thyroid damage, or autoimmune destruction

symptoms: low metabolism, weight gain, cold intolerance, low BP, low HR, fatigue, stunted growth, decreased cognitive function

development of goiter from hypothyroidism

groiter develops bc of lack of negative feedback and low plasma thyroid levels that causes increase in TSH and TRH

causes & symptoms of hyperthyroidism

causes: tumors or autoimmune disease (Graves’ disease)

symptoms: high metabolism, weight loss, increased appetite, heat intolerance, increased HR, anxiety, constant fight-or-flight state, goiter

zona gomerulosa

aldosterone (salt)

• aldosterone regulates Na+ and K+ and blood volume (bc water follows salt)

• cortex and steroid hormone

zona fasciculata

cortisol and small amount of androgens (sugar)

• cortex and steroid hormone

zona reticularis

secretes mostly sex steroids - androgens (sex)

• the androgen, DHEA, contributes to the pubertal growth spurt in both sexes and is important in inducing secondary sex characteristics in females

• cortex and steroid hormone

medulla

epinephrine and norepinephrine

• catecholamines

2 parts of adrenal glands

cortex (3 parts) and medulla

the production of specific adrenal steroid hormones in each zone is determined by which ___ are present in each zone

enzymes

cortisol cascade

3 hormones - CRH, ACTH, cortisol

physiological functions of cortisol (nonstress) (4)

1. metabolic effects - glucose production btw meals

2. permissive of adrenergic receptors in the cardiovascular system

3. anti-inflammatory/anti-immune - prevent hyper-response

4. fetal/neonatal development of brain, intestines, lungs, glands

functions of cortisol in stress (6)

1. metabolic effects - catabolizes body stores of nutrients thereby mobilizing glucose, fatty acids, amino acids for energy and tissue repair

2. bone resorption

3. support sympathetic responses related to vasoconstriction

4. stimulates erythropoietin - replaces RBC’s if bleeding out

5. anti-inflammatory/immunosuppression - prevent rejection of transplanted organ

6. inhibition of non-essential function

andrenal insufficiency

cortisol hyposecretion (lack of cortisol)

primary adrenal insufficiency (Addison’s Disease)

caused by: destruction of adrenal cortex

• primary effector organ

results in: hypotension, low blood glucose, high plasma ACTH and high CRH

secondary adrenal insufficiency

caused by: anterior pituitary dysfunction

• loss of ACTH

results in: similar symptoms as in primary adrenal insufficiency, but with low plasma ACTH

cushing’s syndrome vs disease

Cushing’s syndrome: hypercortisolism and all of its effects, regardless of the original cause

Cushing’s disease: a case of Cushing’s syndrome when the cause is identified as an ACTH-secreting tumor

stress increases the levels of (6)

• aldosterone - increases Na+ retention and BP

• vasopressin - increases water retention and BP

• growth hormone

• glucagon

• beta-endorphin - pain reliever/mood elevation

• epinephrine 

stress decreases the levels of (1)

insulin

• less insulin —> the levels of glucose, fatty acids, and amino acids in the plasma increase

hyperplasia

chondrocytes undergoing cell division (mitosis)

hypertrophy

older chondrocytes enlarging

epiphyseal growth plate

open —> cartilage is still growing

closes at the end of puberty

environmental factors influencing growth (4)

1. adequate nutrition (esp protein)

2. freedom from chronic illness/disease

3. freedom from chronic psychosocial stress

4. sleep

hormonal influences on growth (8)

1. growth hormone

2. insulin-like growth factors (IGFs)

3. insulin

4. thyroid hormone

5. testosterone

6. estrogens/DHEA

7. other peptide growth factors in organs

8. cortisol (anti-growth effects)

growth hormone cascade

hormones - GHRH (+), SST (-), GH, IGF-1

functions of growth hormone (GH)

• promotes postnatal growth 

• metabolic effects

  • mobilize glucose for energy (prevents storage)

  • mobilize fatty acids for energy (lipolysis)

functions of IGF-1

promotes postnatal growth in organs, body-wide, and locally in bone by stimulating hyperplasia and hypertrophy

end result of growth hormone cascade

enhances amount body protein, burns fat, prevents glucose storage, promotes bone and organ growth

dwarfism

bones escify way too early

• growth plates close too early

gigantism

too much GH before epiphyseal plates close

acromegaly

too much GH after epiphyseal plates close

• thickening of bones and heart