CH 23 Endocrine control of growth and metabolism
GROWTH HORMONE origin Factors affecting release Target cells or tissues Whole body or tissue reactions
* Anterior pituitary * Circadian rhythm of tonic secretion; influenced by circulating nutrients & other hormones such as THYROID hormone * Trophic on liver for insulin-like growth factor production; also acts directly on many cells * Bone & cartilage growth; soft tissue growth; increase plasma glucose
What time of day is cortisol @ it's lowest? When does it peak?
* about 3 am * early morning to noon
Symptoms of Hypothyroidism:
* slowed metabolic rate & oxygen consumption, intolerant of cold * decreased protein synthesis, brittle nails, thin hair, dry thin skin, myxedema. * children: slow bone & tissue growth * Nervous system: slowed reflexes, slow speech & thought processes, feelings of fatigue * bradycardia
Thyroid secretes what hormones?
*calcitonin (from C cells) *thyroid hormone (follicular cells)
What are the functions of calcium?
*important signal molecule * intercellular cement that holds cells together at tight junctions * Cofactor in the coagulation cascade * Plasma Ca concentrations affect the excitability of neurons
CALCITONIN function:
*produced by C cells of the thyroid gland Actions are opposite of PTH *released when plasma CA are high to decrease bone resorption, increase renal excretion
Where is cortisol secreted? How is it secreted? Control pathway: Whole body or tissue reaction: Action on cellular level: Feedback regulation:
*secreted in the adrenal cortex *Circadian rhythm/tonic secretions; increase with stress *CRH (hypothal) -> ACTH (ant pituitary) -> cortisol *Increase glucose, decrease immune activity, catabolic *Inc gluconeogenesis, glycogenolysis, blocks cytokines production from immune cells *Negative
What causes Cushing's syndrome?
1) Adrenal Tumor (primary hypercortisolism) 2) Pituitary tumor aka CUSHING's DISEASE 3) Iatrogenic (provider-caused) hypercortisolism
What are the 3 hormones that control calcium balance?
1) Parathyroid hormone 2) calcitriol (Vitamin D3) 3) calcitonin
What are the three types of steroids that the adrenal cortex secrete?
1) aldosterone 2) glucocorticoids (Cortisol is the main one) 3) sex hormones (mostly androgens in men)
The stimulous for GH secretion are integrated in the hypothalamus, which secretes 2 neuropeptides, what are they? What do they do?
1) growth hormone-releasing hormone (GHRH) 2) growth hormone-inhibiting hormone, also known as somatostatin (SS) GHRH from hypothalamus + GH release
what are osteoclasts?
Bone is dynamic. Resorption or breakdown of bone is controlled by osteoclasts (dissolve bone) by secreting HCL acid
What are osteoblasts & what do they do?
Bone-forming cells, produce enzymes and osteoid
What percentage of calcium is in the body's bones?
99%
Addison's disease is a problem with what hormone/s?
A = All adrenal hormones ALSO pigmented skin "tan"
What type of tissue is the adrenal medulla and what does it secrete?
Adrenal medulla is neural tissue (modified sympathetic ganglia), secrete catecholamines (epinephrine)
How do bones grow? What two hormones + bone growth?
As collagen layer thickens -> older cartilage calcifies -> older chondrocytes degenerate, leaves spaces that osteoblasts invade which then lay down bone matrix Growth hormone & insulin-like growth factors
hyperthyroidism can be caused primary cause: secondary cause:
Autoimmune (Graves' disease) Thyroid gland tumor Pituitary tumor
The precursor chemical for ACTH synthesis is a) CRH b) POMC c) Beta-endorphin d) MSH e) TRH
B) POMC
What are osteoclasts?
Large mobile cells, responsible for resorption or breakdown of bone. Dissolve bone (secrete HCL acid)
What is the relationship between tanning, immunity, & appetite?
MSH (melano stimulating hormone) Brain: Inhibits food intake Skin: influence skin color
What is Paget's disease & treatment?
Osteoclasts are overactive & bone is weakened by abnormal resorption. Leads to larger, but weaker bones. Tx: calcitonin to stabilize abnormal bone loss.
What is hyperthyroidism? Symptoms:
Thyroid gland secretes too much hormone. * increased O2 consumption & metabolic heat production, warm sweaty skin, intolerant of heat * increased protein catabolism, muscle weakness, wt loss *Nervous system: hyperexcitable reflexes, irritability, insomnia, psychosis *rapid HR, increased force of contraction due to up-regulation of B1-receptors on the myocardium *Exophthalmos
Where are the adrenal glands located & how many tissues do they have?
Top of kidneys Have 2 distinct tissues (cortex and medulla)
What does the adrenal cortex secrete?
Variety of steroid hormones * zona glomerulosa -> aldosterone * zona fasciculata -> glucocorticoids * zona reticularis -> sex hormones
Where do osteocytes come from? purpose? What is unique about osteocytes in regards to receptors?
When osteoblasts complete their work they revert to less active form called osteocytes * act as mechanosensors, ex. with mechanical stimulus such as weight bearing exercises -> build bone.
The pituitary hormone that triggers the release of thyroid hormone from the thyroid gland is a) TSH b) ACTH c) FSH d) TRH e) CRH
a) TSH (thyroid stimulating hormone)
elevated levels of calcium ion in the blood stimulate the secretion of the hormone a) calcitonin b) thyroid hormone c) parathyroid hormone d) growth hormone e) testosterone
a) calcitonin
Cortisol secretion peaks between ______ and ________ a) early morning & noon b) midnight & early morning c) Noon & early evening d) early evening & midnight
a) early morning and noon
Bill does not begin puberty until he is 16 years old. What effect would you predict this will have on his stature? a) bill will probably be taller than if he had started puberty earlier b) will probably be shorter than if he had started puberty earlier c) will probably be a dwarf d) will have bones that are denser than normal e) the late onset of puberty will have no effect on his stature
a) will be taller than if he had started puberty earlier
When does loss of bone mass begin, what age?
age 30
Without cortisol's permissive effect on _____, an animal would die. a) insulin b) glucagon c) thyroid hormone d) parathyroid hormone e) aldosterone
b) glucagon
Hyperthyroidism a) decreases oxygen consumption b) increases protein catabolism c) decreases protein synthesis d) slows the HR e) causes cold intolerance
b) increases protein catabolism
the parathyroid gland produce a hormone that a) stimulates the formation of wbc b) increases the level of calcium ions in the blood c) increases the level of Na in the blood d) increases the level of potassium ions in the blood e) increases the level of glucose in the blood
b) increases the level of calcium ions in the blood
Somatostatin is another name for a) growth hormone b) growth hormone releasing hormone c) growth hormone-inhibiting hormone d) thyroid hormone e) parathyroid hormone
c) growth hormone-inhibiting hormone
What is Cushing's syndrome
cause: high levels of cortisol sx: moon face, upper body weight gain (including upper back), striations
What are chondrocytes
collagen-producing cells
May result from pituitary tumor
cushing's disease
Excessive growth hormone during adulthood will cause a) goiter b) exopthalamus c) giantism d) acromegaly e) diabetes
d) acromegaly
Damage to cells of the zona fasciculata of the adrenal cortex would result in a) the disappearance of axillary and pubic hair b) increased volume of urine formation c) decreased levels of sodium ion in the blood d) decreased ability to convert lipids to glucose e) increased water retention
d) decreased ability to convert lipids to glucose
Crossover effects are sometimes seen among a) most hormones b) all hormones c) peptide/protein hormones d) steroid hormones
d) steroid hormones
What is CRETINISM?
decreased mental capacity (from hypothyroid)
Cortisol a) suppresses the immune system b) causes a positive calcium balance c) influences brain function d) A & B e) A & C
e) A and C
The endocrine gland that is a modified sympathetic ganglion is the a) thyroid b) anterior pituitary c) posterior pituitary d) adrenal cortex e) adrenal medulla
e) adrenal medulla
Cholesterol is a precursor for the synthesis of a) progesterone b) aldosterone c) estradiol d) two of the above e) all of the above
e) all of the above
A rise in cortisol would cause each of the following except one. Identify the exception: a) enhanced rate of glucose synthesis by the liver b) increased rate of glycogen usage by the liver c) higher levels of fatty acids in the blood d) suppression of the immune system e) increased ACTH levels
e) increased ACTH levels
What is hypothyroidism
hyposecretion of thyroid hormone
Thyroid gland is butterfly shaped gland & is located where?
just below the larynx
What are the 2 layers of bone?
outer dense COMPACT bone inner layer of spongy TRABECULAR bone
All steroid hormones are synthesized from what?
Cholesterol
Hypercortisolism
Cushing's disease
POMC is a precursor to what?
ACTH & MSH
Where do long bones get longer? Which area?
Epiphyseal plates
What is goiter caused from?
Excessive + of thyroid gland by TSH causes the thyroid to enlarge
hyperthyroidism
Graves' disease
involves endocrine stimulation by antibodies
Graves' disease
What is the most common cause of hyperthyroidism?
Graves' disease (auto immune disease) Body produces AB called thyroid stimulating immunoglobulins (TSI). They mimic the action of TSH by combining on receptors on the thyroid gland -> goiter.
What does the hormone CALCITRIOL (vit D3) do?
Intestinal absorption of calcium is enhanced by the action of calcitriol/vit D3. The body makes it through vitamin D that has been ingested or absorbed via skin. *enhances Ca uptake from small intestine *decreased plasma Ca -> PTH secretion which -> + calcitriol synthesis *negative feedback loop via increase plasma CA ***ANYTHING that shuts of PTH also shuts this off***
What are thyroid hormones made from?
Iodine & tyrosine
Causes of primary hypothyroidism:
Lack of iodine in the diet Hashimoto's thyroiditis (autoimmune disease)
PARATHYROID HORMONE (PTH) origin: factors affecting release: target cells or tissues: target receptor: whole body or tissue reaction: Action at cellular level: Feedback regulation:
Parathyroid decrease plasma calcium kidney, bone, intestine membrane receptor acts via cAMP Increase Plasma Ca Inc vitamin D synthesis, inc renal reabsorption, in bone negative via increased plasma CA
What is bone resorption?
Process that osteoclasts break down bones & release the minerals, resulting in transfer of calcium into the blood
What is the most important metabolic effect of cortisol?
Protective effect against hypoglycemia, especially during stress.
What does the hormone PTH do?
Purpose of it is to increase plasma Ca concentrations. Acts on: bone via *osteoclasts*, kidney, intestine Negative feedback loop
GROWTH HORMONE aka SOMATOTROPIN is released throughout life. Peak GH occurs @ what age?
Teenage years
THYROID HORMONES Cell of origin: Factors affecting release: Control pathway: Target cells or tissue: Target receptor: Whole body or tissue reaction: Feedback regulation:
Thyroid follicle cells Tonic release TRH (hypothalamus) ->T3 + T4 (thyroid) -> T4, deiodinates in tissues to form more T3 Most cells of the body Nuclear receptor * Inc oxygen consumption (thermogenesis) * Protein catabolism in adults (anabolism in kids) * Normal development of nervous system Free T3 & T4 have negative feedback on anterior pituitary & hypothalamus
