a&p ch 16
chromafin cells
(adrenal medulla) secrete epinepherine and norepinephrine
Trophic hormones
(which induce growth in target cells); note that some hormones have both tropic and trophic effects on target cells
Thyroid-stimulating hormone (TSH, thyrotropin)—
--ANTERIOR PITUITARY stimulates development of thyroid gland and its secretions, (thyroid hormones); release stimulated by hypothalamic thyrotropin-releasing hormone (TRH)
Adrenocorticotropic hormone (ACTH, corticotropin)—
-ANTERIOR PITUITARY stimulates development of adrenal gland and synthesis of various steriod hormones; release is stimulated by hypothalamic corticotropin-releasing hormone (CRH)
Prolactin (PRL)
-ANTERIOR PITUITARY —stimulates growth of mammary gland tissue, initiates milk production after childbirth, and maintains milk production during breastfeeding Release stimulated by hypothalamic prolactin-releasing hormone Inhibited by prolactin-inhibiting factor (dopamine)
-Follicle-stimulating hormone (FSH; gonadotropin)
-ANTERIOR PITUITARY Male—stimulates cells of testes to produce chemicals that bind and concentrate testosterone; under direction of GnRH Female—FSH and LH together trigger production of estrogen; FSH also triggers maturation of ovarian follicles (house developing oocytes)
Mechanisms of Hormone Action: hydrophobic
-Hormone crosses plasma membrane; interacts with receptors in cytosol or nucleus -Hydrophobic hormone forms complex with its receptor; generally interacts with DNA of target cell -Complex exerts effects by changing rate of protein synthesis of one or more proteins
Mechanisms of Hormone Action: hydrophilic -5 steps
-Hydrophilic hormone (first messenger) binds to receptor in plasma membrane -Receptor activates peripheral protein (G-protein in example) -G-protein activates enzyme; enzyme catalyzes formation of second messenger; initiates series of events in cell that leads to changes in its activity -Adenylate cyclase—example of enzyme activated by G-protein second-messenger system; catalyzes formation of second messenger cyclic adenosine monophosphate (cAMP) -cAMP initiates changes in cell including activation of protein kinases; catalyzes transfer of phosphate group from ATP to another molecule (phosphorylation) -picture on slide 24
Growth hormone (GH; somatotropin) Short-term effects—generally metabolic
-Promotion of fat breakdown -Generation of new glucose in liver -Inhibition of glucose uptake by muscle fibers -All increase blood glucose and fatty acid levels; can be used by cells for fuel and raw materials for growth
receptor location: Hydrophobic hormones
-able to cross through plasma membrane; generally interact with receptors in cytosol or nucleus
Hypothalamic-hypophyseal portal system—
-specialized blood supply; allows both hypothalamus and pituitary to deliver hormones directly to target cells -Tiny capillaries merge in hypothalamus; form larger portal veins that travel through infundibulum -Portal veins lead to second group of capillaries in anterior pituitary gland -Systems like this, in which capillaries are drained by veins that lead to another set of capillaries, are called portal systems
TIERS IDK
1) First tier—neuroendocrine cells of hypothalamus secrete releasing and inhibiting hormones in response to change in homeostatic ________________ (tropic hormones) 2) Second tier—tropic hormones' effect on anterior pituitary; stimulates or inhibits anterior pituitary hormone secretion 3) Third tier—actions of anterior pituitary hormones at target tissues; target tissue glands secrete hormones that can affect various homeostatic variables -Once homeostatic variable that stimulated activity at hypothalamus returns to normal set point, change is detected at hypothalamus; stops secreting tropic hormones -Anterior pituitary changes hormone secretion accordingly; target tissues follow suit and feedback loop is closed
Effects of thyroid hormone three main categories
1) Regulation of metabolic rate and thermoregulation-set basal metabolic rate (amount of energy required by body at rest) 2) Promotion of growth and development: —thyroid hormones are required for normal bone growth, muscle growth, and nervous system development 3) Synergism with sympathetic nervous system— increases in thyroid hormone levels act on target cells of sympathetic nervous system Increases (up-regulate) receptors for sympathetic neurotransmitters Affects regulation of blood pressure, heart rate, and other sympathetic activities
regulation of hormone secretion: feedback loop
1)Stimulus—regulated physiological variable deviates from normal range 2) Receptor—receptors on target cells detect deviation of variable 3) Control center—stimulated control center (often endocrine cell) increases or decreases secretion of particular hormone 4) Effector/response—hormone triggers response in its target cells; moves conditions toward normal range 4) Homeostatic range—as variable returns to its normal range, feedback to control center decreases response
Thyroid Hormone production: 4 steps
1. 1) iodide ions and thyroglobulin are secreted into the colloid 2. 2) iodide ions are converted to iodine atoms that attach to thyroglobulin 3. 3) iodinated thyroglobulin enters the follicle cell by endocytosis and T3 and T4 are cleaved from the molecule in reactions catalyzed by lysosomal enzymes 4. 4) t3 and t4 are released into the blood
A major determinant of a hormone's mechanism of action is __________. a. whether the hormonal molecule is hydrophobic or hydrophilic b. its size c. whether it is rapid acting or slow acting d. if it activates gene activity or not
A
The hypothalamic-hypophyseal portal system A) allows hypothalamus to deliver hormones directly to target cells B) is similar to the arrangement of vessels found in many other tissues C) includes capillaries that travel through the infundibulum D) includes capillaries are drained by arteries that lead to another set of capillaries E) none of these choices is correct
A
Which of the following is a function of luteinizing hormone? A) triggers release of an oocyte during ovulation B) triggers rapid protein synthesis and cell division C) stimulates cells of testes to produce chemicals that bind and concentrate testosterone D) allows for insertion of water channels cells of kidney tubules E) triggers development of secondary sex characteristics at puberty
A
Which of the following layers of the adrenal cortex is matched correctly? a) zona reticularis - synthesizes androgens b) zona glomerulosa - synthesizes cortisol c) zona fasciculata - synthesizes aldosterone
A
Which of the following is NOT a true statement? a) most hormone systems function under a positive feedback system b) secretion of hormones occurs in short bursts c) signals from the nervous system regulate hormone secretion d) chemical changes in the blood may determine concentration of hormone release e) regulation of secretion prevents overproduction of a hormone
A -ITS NEGATIVE FEEDBACK NOT POSITIVE
osteoporosis
A condition in which the body's bones become weak and break easily.
Luteinizing hormone (LH; gonadotropin)
ANTERIOR PITUITARY Luteinizing hormone (LH; gonadotropin) Male—stimulates production of testosterone by testes under direction of hypothalamic gonadotropin-releasing hormone (GnRH) Female—stimulates production of estrogen and progesterone from ovaries; triggers release of oocyte in ovulation; also under direction of GnRH
Which of the following statements is NOT true about the thyroid gland? a) most of the gland is made up of sacs called thyroid follicles b) the parafollicular cells produce thyroxine c) the lobes are connected by an isthmus d) it is the only endocrine gland that stores hormones in large amounts e) hormones secreted control the basal metabolic rate (BMR)
B
Hydrophobic hormones half lives
have longest half-lives—often week or more—due to extensive protein binding
Hydrophilic hormones half lives
have relatively shorter half-lives; smallest having half-lives of few minutes to seconds
antagonists
hormones that act on the same cells but have opposite effects
Addison's disease
hyposecretion of cortisol a condition that occurs when the adrenal glands do not produce enough cortisol or aldosterone
what does calcitonin do
inhibits osteoclasts and allows for osteoblast activity -
Glucagon target cells:
liver cells muscle tissue and adipose tissue promotes reactions that increase levels of glucose and metabolic fuels in blood: Breakdown of glycogen (glycogenolysis) Formation of new glucose (gluconeogenesis) in liver
Regulation of hormone secretion: Humoral stimuli
many endocrine cells respond to concentration of certain ion or molecule in blood or extracellular fluid
how is production of t3 and t4 regulated?
negative feedback loop with three tiers
secondary hypothyroidism
problem at pituitary not the thyroid low TSH low t3 and t4
primary hypOrthyroidism
problem at the thyroid not the pituitary TSH high T3 and T4 low
Hormones—
secreted into blood to affect distant targets; known as classic endocrine signals
Delta cells—secrete peptide hormone....
somatostatin
Regulation of hormone secretion: Hormonal stimuli
some endocrine cells increase or decrease secretion in response to secretion of other hormones
Regulation of hormone secretion: neural stimuli
some endocrine cells respond to signals from nervous system
Growth hormone-releasing hormone (GHRH)—
stimulates release of GH; secretion increases during exercise, fasting, and stress, and after ingestion of protein-rich meal
UP regulation
the target cell increases the number of receptors that it is displaying typically happens when levels of a hormone go down in the blood stream sometimes happens as a temporary response to an increase of hormones in the blood
Hyperthyroidism symptoms
weight loss, heat intolerance, disruptions in blood pressure and heart rhythms, and development of goiter and exophthalmos (enlargement of thyroid gland and protruding eyeballs, respectively)
when is calcitonin needed
when blood calcium level is to high (hypercalcemia)
Half-life
—amount of time it takes for plasma concentration of hormone to reduce by half
Hyperglycemia
—blood glucose levels are too high; common causes of chronic hyperglycemia:
receptor location; Hydrophilic hormones
—cannot readily cross plasma membrane; generally interact with receptors embedded in target cell's plasma membrane
Paracrine
—chemicals secreted by cells into extracellular space; affect nearby but different types of cells
Autocrine
—chemicals secreted by cells into interstitial fluid; elicit effects from same cell or cell type
Renin
—converts plasma protein angiotensinogen to angiotensin I; vital component of renin-angiotensin-aldosterone system, which maintains blood pressure
Congenital hypothyroidism (cretinism)
—develops when infant is born with inadequate thyroid function; can lead to delayed physical and nervous system development; potentially mental retardation if left untreated
Diabetes insipidus caused by
—disease caused by the lack of ADH secretion or activity; causes extreme thirst and signs of dehydration; body is unable to conserve most water consumed
Iatrogenic Cushing's syndrome
—disorder caused by long-term administration of glucocorticoid-containing products
Bound hormones
—form complexes with binding proteins in plasma; usually hydrophobic; do not associate with water molecules in plasma -Allow hydrophobic hormones to be transported safely through watery environment of blood Reservoir of hormones; can be released when needed; help prevent large fluctuations in concentration of free hormone in plasma -Extends lifespan of hormone in blood (discussed later in section on half-life) -exception thyroid hormones
Acromegaly
—hypersecretion of GH after epiphyseal plate closure; most affected are tissues of head, face, hands, and feet, as well as liver and heart; progressively distorts organs; can lead to heart failure
Gigantism
—hypersecretion of GH before epiphyseal plates have closed; leads to extremely tall individuals; excess GH also increases size of other tissues (heart)
Parafollicular cells WHAT DO THEY PRODUCE?
—in spaces between adjacent thyroid follicles; large cells that produce hormone calcitonin
Parathyroid hormone (PTH)
—major factor in maintenance of blood calcium ion concentration; secreted in response to declining calcium ion levels in blood; triggers following effects: Increases release of calcium ions from bone by stimulating osteoclast activity Increases absorption of dietary calcium ions by small intestine
Graves' disease
—most common hyperthyroidism; immune system produces abnormal proteins that mimic actions of TSH on thyroid gland
Posterior pituitary (neurohypophysis)
—nervous tissue ("neuro")
Cushing's disease
—oversecretion from adrenal cortex, usually from tumor
Oxytocin
—produced by hypothalamus; stored in axon terminals of posterior pituitary gland (Figure 16.9b) -Functions primarily focused on reproduction -Target cells are in mammary glands of breast tissue and smooth muscle of uterus -In nursing mother, suckling stimulates oxytocin release; causes mammary glands to contract resulting in milk ejection
Colloid
—protein-rich, gelatinous material; contains precursor for thyroid hormone and high concentration of iodine atoms; both important to thyroid hormone synthesis
Erythropoietin (EPO)
—secreted by specific kidney cells in response to decreased blood oxygen levels; acts on red bone marrow to stimulate development of new erythrocytes (erythropoiesis); increases oxygen-carrying capacity of blood
Thyroid gland
—secretes thyroid hormone and calcitonin -Anterior neck, just superficial to laynx -Butterfly-shaped; consists of right and left lobes connected by isthmus (small band of thyroid tissue)
Hypothalamus
—small anteroinferior portion of diencephalon; connected to pituitary gland by stalk
Pituitary gland
—small organ; sits in sella turcica of sphenoid bone; composed of two structurally and functionally distinct components ANTERIOR AND POSTERIOR
Free hormones
—small, amino acid-based hormones; hydrophilic and able to freely associate with water; travel freely through water-based plasma of blood Note: Few hydrophilic hormones, such as growth hormone (anterior pituitary gland), are protein-bound
Down-regulation
—target cells decrease number of receptors displayed in response to prolonged exposure to high level of hormone in blood -protects cell from over response
Anterior pituitary (adenohypophysis)
—true gland; hormone-secreting glandular epithelium ("adeno")
Growth hormone (GH; somatotropin) LONG-term effects
Long-term effects—not all directly mediated by GH; GH acts on liver and other target tissues to promote production of hormone insulin-like growth factor (IGF) (Figure 16.11) Affects nearly every cell in body; triggers rapid protein synthesis and cell division leading to increased longitudinal bone growth and muscle development in children Decreases blood glucose ("insulin-like") concentration in blood by stimulating glucose uptake by cells; in opposition to initial actions of GH GH + IGF continue to play important roles in adults; promote muscle development as well as regulation of body mass
Symptoms of cortisol excess:
MOON FACE Lipolysis releases fatty acids from upper and lower limbs, which become slim; deposited in adipose tissue in characteristic places: Trunk Face (causing round face called moon facies) Back of neck (producing "buffalo hump") Breakdown of protein in muscles leads to muscle wasting; released fats and amino acids are converted into glucose, causing hyperglycemia Slight mineralcorticoid effect causes hypertension Effect on leukocytes causes immunosuppression Effect on osteoblast activity and calcium absorption may cause osteoporosis
hormones
Maintain fluid, electrolyte, and acid-base homeostasis Promote GROWTH Regulate metabolic reactions
endocrine organs; primary
Primary organs—only endocrine functions
12) Which of the following is NOT consistent with an overproduction of ADH? A) Decreases urine production B) Increases circulating blood volume C) Decreased blood pressure D) Increased conservation of water from the renal filtrate E) none of these choices is correct
C
Adrenal insufficiency a) is characterized by hypersecretion of both cortisol and aldosterone b) is known as Cushing's disease c) may result in fluid, electrolyte, and acid-base homeostasis disruptions d) may result in hyperglycemia and hypopigmentation e) none of these choices is correct
C
As we age, the decrease of which hormone is associated with the loss of muscle tissue? a) cortisol b) aldosterone c) human growth hormone d) estrogen e) thyroxine
C
Which gland is divided into two distinct functional units? a) thyroid b) pineal c) pituitary d) thalamus e) Hypothalamus
C
Which gland or organ is not strictly classified as a primary endocrine gland? a) Thyroid b) Adrenal cortex c) Heart d) Parathyroid e) Anterior pituitary
C
Which of the following is a TRUE statement? a) the levels of glucagon and insulin are based on a positive feedback system b) hyperglycemia stimulates release of glucagon c) insulin increases glycogenesis and lipogenesis d) glucagon stimulates kidney cells to releases glucose into the blood e) blood amino acid level is the most important regulator of insulin and glucagon
C
Which of the following is an effect of the thyroid hormones? a) increases blood cholesterol b) increases carbohydrate synthesis c) increases oxygen consumption d) decreases actions of the epinephrine and norepinephrine e) helps slow down body growth
C
Which of the following is true? a) the hypothalamic hypophyseal tract contains fibers that connect the hypothalamus to the anterior pituitary b) the neurohypophysis synthesizes oxytocin and antidiuretic hormone c) vasopressin (ADH) increases blood pressure d) the adenohypophysis stores and releases two hormones
C
Angiotensin II a) inhibits aldosterone release b) decreases blood pressure c) is made by converting enzyme in kidneys d) reabsorbs water and salt in kidneys e) is a potent vasodilator
D
Chronic hyperglycemia does NOT A) damage peripheral nerves leading to peripheral neuropathy B) increase risk of heart attack, nonhealing wounds, and amputation C) damage blood vessels resulting in decreased circulation to tissues D) increase fuel availability for ATP production E) all of these are caused by chronic hyperglycemia
D
Which of the following is TRUE when describing the permissive effect of a hormone? a) a permissive hormone can cancel out the effect of another hormone b) this means that two hormones have a greater effect than just one c) the hormone can act alone when having an effect on a tissue d) is usually the result of a second hormone's exposure on target cells
D
Which of the following is the excess of human growth hormone AFTER puberty? a) gigantism b) achondroplasia c) pituitary dwarfism d) acromegaly e) none of these choices is correct
D
Which statement is CORRECT regarding the relationship between the hypothalamus and pituitary gland? a) releasing hormones are secreted by the anterior pituitary b) the hypothalamus is 'controlled' by the pituitary gland c) the posterior lobe of the pituitary secretes inhibiting hormones d) the hypothalamus secretes releasing and inhibiting hormones that influence the pituitary gland
D
Which statement is NOT true of the interplay between PTH and calcitriol? a) calcitriol increases calcium absorption from foods b) PTH increases resorption of bone c) high blood calcium levels increases calcitonin release d) PTH decreases vitamin D levels e) PTH raises blood calcium levels
D
Which chemical class of hormones is NOT matched correctly with its solubility? a) Aldosterone - lipid soluble b) Steroid hormone - lipid soluble c) Growth hormone - water soluble d) Thyroid hormone - water soluble e) Catecholamines - water soluble
D THYROID HORMONES ARE CLASSIFIED/MADE FROM AN AMINO ACID CALLED TYROSINE
type 2 diabetes
Diabetes of a form that develops especially in adults and most often obese individuals and that is characterized by high blood glucose resulting from impaired insulin utilization coupled with the body's inability to compensate with increased insulin production.
Which of the following hormones would increase in a laboratory animal after a thyroidectomy? 1. thyroid stimulating hormone (TSH) 2. triiodothyronine (T3) 3. thyrotropin-releasing hormone (TRH) 4. thyroxine (T4) a) 1 only b) 2 only c) 3 only d) 4 only e) 1 and 3
E
Which of the following hypothalamic hormones causes the release of ACTH? a) TRH b) FSH c) LH d) GHRH e) CRH
E
Which of the following is a TRUE statement in reference to melatonin? 1. it is secreted by the pineal gland 2. it is stimulated by sunlight 3. it is a derivative of serotonin 4. it increases the production of melanin a) 1 only b) 2 only c) 3 only d) 4 only e) 1 and 3 are correct
E
Which of the following statements is TRUE? a) a carbohydrate-rich meal increases insulin secretion b) a protein-rich (low carb) meal increases glucagon secretion but a carbohydrate-rich meal decreases glucagon secretion c) parasympathetic stimulation increases insulin secretion d) exercise (sympathetic stimulation) will increase glucagon secretion e) all of the statements are true
E
Exocrine acinar cells
EXOCRINE cells in the pancreas —clustered around small ducts into which they secrete enzymes and other products; delivered to digestive tract
Aldosterone activates hydrogen ion pumps that transport hydrogen ions from the fluid of the renal tubules into the extracellular fluid. T OR F
FALSE
Most hydrophilic hormones must be attached to a transport protein in order to be circulated through the blood stream. T OR F
FALSE
People under a great amount of chronic stress are no more prone to disease than those who are not. T OR F
FALSE
T3 and T4 are water soluble and thus cannot diffuse through the plasma bilayer. T OR F
FALSE
The adrenal medulla has tissue similarities with parasympathetic ganglia. T OR F
FALSE its sympathetic
The stress response is primarily regulated by the pituitary gland. T OR F
FALSE adrenal gland
3 tier negative feedback loop
First tier involves thyrotropin-releasing hormone (TRH) from hypothalamus; second tier is thyroid-stimulating hormone (TSH) from anterior pituitary gland Third tier Production and secretion of TRH and TSH increase when Levels of free T3 and T4 fall Body is exposed to cold temperatures Secretion of TRH and TSH is inhibited by rising levels of free T3 and T4; TSH is also inhibited by somatostatin
Regulation of cortisol involves HPA axis and multi-tiered control mechanism:
First tier—CRH is secreted daily from hypothalamus in rhythmic fashion; peak CRH levels generally in morning Second tier—CRH stimulates ACTH release from anterior pituitary Third tier—ACTH stimulates cortisol production and secretion from adrenal cortex (same peak; blood level tests are timed) Elevated cortisol levels suppress release of CRH and ACTH, closing negative feedback loop associated with HPA axis
Pituitary dwarfism—
GH hyposecretion Leads to individuals that are short in stature but with otherwise proportional limbs and trunk NOT achondroplasia)
Alpha cells—secrete peptide hormone....
Glucagon
Growth hormone is regulated by two hypothalamic hormones -what are they?
Growth hormone-releasing hormone (GHRH)— and somatostatin
Hypersecretion of aldosterone (hyperaldosteronism) can lead to
Hypokalemia (low blood potassium ion level) Hypernatremia (high blood sodium ion level) Hypertension (high blood pressure) Hyposecretion (will be discussed later)
endocrine organs; secondary
Secondary organs—both endocrine and variety of non-endocrine functions
Effects of hormone actions:
Stimulating secretion from endocrine or exocrine cell Activating or inhibiting ENZYME Stimulating or inhibiting mitosis and/or meiosis Opening or closing ion channels in cell's plasma membrane and/or altering its membrane potential Activating or inhibiting transcription of genes that code for RNA or proteins (gene expression)
Milk let-down reflex—example of positive feedback loop (Feedback Loops Core Principle)
Suckling induces lactation, causing more suckling and more milk release Loop ceases when satisfied infant stops suckling
Hypoglycemia—blood glucose levels are too low; can be caused by elevated insulin levels SYMPTOMS
Symptoms—weakness, dizziness, rapid breathing, nausea, and sweating Severe hypoglycemia can lead to confusion, hallucinations, seizures, coma, and death; ensues as brain is deprived of adequate glucose (primary fuel for its metabolic reactions)
Hypothyroidism symptoms
Symptoms—weight gain, cold intolerance, slow heart rate, low blood pressure, and goiter; can be due to immune system disorder or lack of available iodine
Down-regulation makes a target cell less sensitive to a hormone. T OR F
TRUE
The male and female gonads are considered reproductive and endocrine organs. T OR F
TRUE
where a hormone receptor is depends on what?
The chemical nature of a hormone
Antidiuretic hormone (ADH; vasopressin):
Water retention; controls water balance Produced continually in low amounts by hypothalamic neurons Transported through axons in infundibulum to axon terminals in posterior pituitary; stored in synaptic vesicles Axon terminals do not have synapses; instead release ADH into blood vessels when stimulated by action potentials ADH allows for insertion of water channels (aquaporins) into plasma membranes of kidney tubule cells Water passes into cytosol of cells, then back into extracellular fluid and finally to blood; would otherwise have been eliminated from body in urine Diabetes insipidus—disease caused by the lack of ADH secretion or activity; causes extreme thirst and signs of dehydration; body is unable to conserve most water consumed
synergist
act on the same target cell and have the same effect
Growth hormone (GH; somatotropin)
anterior pituitary -—produced and secreted by somatotrophs; releases GH periodically throughout day; peak secretion during sleep Main function is to regulate growth of various target tissues including skeletal and cardiac muscle, adipose, liver, cartilage, and bone Can be either short or long-term effects decreases as we age
parafollicular cells secrete and produce
calcitonin
cortisol
causes blood sugar to go up because of glucogenisis breaks down fat and protein immunosupressent-effects the # of leukocytes (wbc) reduces inflammation (that is why its used as medications)
RAAS is stimulated by WHAT?
decrease in blood volume and/or blood pressure - as in cases of dehydration or hemorrhage (causes decreased renal perfusion)
type 1 diabetes mellitus symptoms
diabetes in which there is no beta cell production of insulin--the patient is dependent on insulin for survival polyuria (frequent urination) and polydipsia (excessive thirst)
growth hormone imbalances list 3
gigantism acromegaly pituitary dwarfism
Blood levels of glucose or calcium represents which type of endocrine regulation? A) Neural stimulation B) Humoral stimulation C) Hormonal stimulation D) Inflammatory stimulation E) None of these
B
What is NOT a function of parathyroid hormone? a) increase formation of vitamin D b) increase the number of osteoclasts c) regulate the level of calcium in the blood d) increase bone resorption e) promote formation of calcitriol
B
Which hormone is NOT matched correctly with its principal action? a) LH - ovulation b) aldosterone- decreases blood pressure c) cortisol - stress response d) thymosin-stimulates development of T lymphocytes e) progesterone - prepares uterine lining
B
two neurohormones are produced by hypothalamus then stored and released from posterior pituitary what are they?
Antidiuretic hormone (ADH) Oxytocin
Beta cells—secrete protein hormone....
Insulin
Parathyroid glands WHAT CELL DOES IT HAVE?
Parathyroid glands—typically 3-5 separate glands; on posterior surface of thyroid gland; secrete parathyroid hormone from chief cells
Thyroid hormones (T3 and T4)
Thyroid hormone consists of amino acid core bound to either 3 (triiodothyroxine, T3) or 4 (thyroxine, T4) iodine atoms Both T3 and T4 are physiologically active but T3 much greater so; T4 is commonly converted to T3 in some target tissues
