Exam 1 Flashcards
chemical messenger system comprising of feedback loops of hormones released by internal glands of the body directly into the blood, regulating distant target organs, functions to maintain homeostasis through the release of hormones by endocrine glands, works together with autonomic nervous system and is integrated by the hypothalamus
endocrine system
chemical synthesized by certain cells and released directly into the blood, produces its effect on cells distant from the site of release
hormones
short or long chains of linked amino acids, water soluble, all pituitary hormones and hypothalamic releasing factors EXCEPT dopamine
peptide and protein hormones
derived from cholesterol, fat soluble, cortisol, testosterone, estradiol
steroid hormones
amino acids with modified groups, water or fat soluble, thyroid hormones, epinephrine, dopamine
amine hormones
cell surface receptors for peptide and water soluble amines that interact with cell surface receptors, signal transduction via second messengers, alteration in cell activity, quick onset and short duration of action
receptors for water soluble hormones
nuclear receptors for steroid and thyroid (fat soluble amine) hormones that diffuse through the plasma membrane, hormone binds with receptor in cytoplasm forming a receptor hormone complex, receptor hormone complex enters the nucleus and triggers gene transcription, transcribed mRNA is translated into proteins that alter cell activity, late onset (because has to make protein) and long duration of action
receptors for lipid soluble hormones
master regulators of the endocrine system
hypothalamus and pituitary
______ produces releasing factors that regulate the following _______ hormones:
1. Growth hormone (GH)
2. Prolactin (PRL)
3. thyroid stimulating hormone (TSH)
4. adrenocorticotropic hormone (ACTH)
5. follicle stimulating hormone (FSH)
6. luteinizing hormone (LH)
hypothalamus, anterior pituitary
________ releases two hormones that are synthesized by the _________:
1. vasopressin
2. oxytocin
posterior pituitary, hypothalamus
- replacement therapy for hormone deficiency states
- antagonists for diseases that result in hypersecretion
- diagnostic tools for identifying endocrine abnormalities
drugs to treat hypothalamic and pituitary disorders
- hypothalamus releases growth hormone releasing hormone (GHRH) which ____________ GH release and somatostatin which __________ GH release
- anterior pituitary –> GH release by GHRH
- liver –> GH ________ IGF-1 production
stimulates, inhibits, stimulates
GH has negative feedback on which endocrine gland?
pituitary
IGF-1 has negative feedback on which endocrine glands?
pituitary and hypothalamus
releasing factor secreted by the hypothalamus to stimulate GH secretion from anterior pituitary
growth hormone releasing hormone (GHRH)
- synthetic N-terminally modified form of human GHRH, resistant to degradation for prolonged duration of action (whereas giving human GHRH easily broken down by enzymes) to increase GH and IGF-1
- clinical use is for reduction of excess abdominal fat in HIV-associated lipodystrophy but not for GH deficiency
- administered SC
- adverse effects: hypersensitivity, joint pain/arthralgia, muscle pain/myalgia, peripheral edema, hyperglycemia, injection site reactions
tesamorelin acetate (EGRIFTA SV)
how must all peptide hormones be administered?
SC
- peptide hormone secreted by somatotroph cells of anterior pituitary, most abundant pituitary hormone that is released in a pulsatile fashion, maximal at night at deep sleep, other stimuli include high protein meals, exercise, stress, hypoglycemia
- in childhood/adolescence this is required for attainment of normal size (deficiency in childhood means dwarfism)
- in adult life has important effects on carbohydrate/lipid metabolism and on lean body mass and bone density
- effects of this are mediated by IGF-1 released from the liver
growth hormone (GH)
increased glucose synthesis and release which increased blood glucose (can lead to hyperglycemia), increased lipolysis (fat breakdown), stimulates protein synthesis for increased muscle growth, increased longitudinal growth until puberty, increased bone mineral density after puberty
pharmacological effects of GH
short stature and low growth rate caused by decreased GHRH for hypothalamic version of this or decreased GH for pituitary version of this, proportional decrease in size of all body parts, treatment includes somatropin (GH analog)
dwarfism
inherited, relatively rare, defective GH receptors in liver (inadequate IGF-1 production), like the other form but plasma GH levels are normal or increased whereas IGF-1 levels are decreased, liver can’t produce IGF-1 b the because GH receptors on the liver are defective, treatment includes mecasermin (IGF-1 analog)
Laron dwarfism
- recombinant human GH preparations that are modified in some way to decrease breakdown by enzymes, restores normal growth and metabolism in GH-deficient individuals
- clinical uses: replacement therapy as daily SC injection for GH deficiency in children (varies in adults) or to treat AIDS-induced wasting syndrome which is a severe loss of muscle mass due to AIDS (because GH increases muscle mass)
- adverse effects: well tolerated, rare intracranial hypertension, arthralgia, myalgia, peripheral edema, HYPERGLYCEMIA main adverse effect –> SHOULD NOT be given to patients with active malignant tumors or a history of recurrent tumor growth
somatropin (HUMATROPE, NUTROPIN, GENOTROPIN)
- MOA: recombinant IGF-1 analog that stimulates IGF-1 receptors and improves growth (bone) and metabolic effects (increased muscle mass, decreased body fat) mediated by IGF-1
- clinical use: replacement therapy as SC injection in iGF-1 deficiency/Laron dwarfism that is not responsive to exogenous GH
- adverse effects: hypoglycemia (because IGF-1 analog and IGF-1 is insulin like and insulin causes hypoglycemia), rare intracranial hypertension –> to AVOID HYPOGLYCEMIA, patients should take with a carbohydrate containing meal/snack 20 minutes before or after taking drug –> SHOULD NOT be given to patients with active malignant tumor or history of recurrent tumor growth
mecasermin (INCRELEX)
- excessive secretion of GH (usually from pituitary adenoma –> tumor)
- before puberty causes gigantism in children (person is very large but proportional)
- after puberty acromegaly in adults, disproportionate growth of the body due to bone thickening not getting any longer, slow onset
- treatment options: transsphenoidal surgical resection, radiation therapy, pharmacological includes drugs that inhibit GH secretion (somatostatin analogs, dopamine agonists) or block GH action (GH receptor antagonist) –> pharmacological therapy is considered when surgery or radiation is contraindicated
syndromes of GH excess
- the human form of this inhibits GH release but not useful clinically because has 1-3 min half life, analogs substitute D amino acids (unnatural ones) so enzymes can’t recognize as quickly
- MOA: inhibit GH release with higher potency than what it is an analog for, normalize GH and IGF-1 levels in 60-80% of patients
- mainstay drugs given SC or IM to treat acromegaly
- adverse effects: GI disturbances, GALLSTONES (decreases bile secretions) main adverse effect, sinus bradycardia, conduction abnormalities
somatostatin (SST) analogs: octreotide (SANDOSTATIN), lanreotide (SOMATULINE), pasireotide (SIGNIFOR)
- MOA: decrease GH release in acromegaly patients, advantage is that they are administered orally, disadvantage is that they are less effective than other drugs that decrease GH release (normalize GH and IGF-1 levels in only 10-30% of patients)
- used orally as second-line agents
- adverse effects: nausea, headache, orthostatic hypotension
dopamine (DA) agonists: bromocriptine (PARLODEL), cabergoline (DOSTINEX)
which is more advantageous (because it has less GI side effects and has more convenient once to twice weekly dosing), cabergoline or bromocriptine?
cabergoline
- MOA: pegylated mutant GH analog, acts as competitive GH receptor antagonist that prevents GH receptor activation and inhibits IGF-1 production, blocks site but doesn’t activate so no IGF-1 secretion, pegylation prolongs drug’s half life and allows for once daily SC dosing
- CAUTION: may increase growth of GH-secreting adenomas so annual pituitary MRI is recommended for patients taking this (blocks whole feedback in hypothalamus so it doesn’t stop releasing GH)
- adverse effects: increased liver enzymes (hepatotoxicity, requires monitoring of liver function)
GH receptor antagonist: pegvisomant (SOMAVERT)
- peptide hormone secreted by lactotrophs of the anterior pituitary gland
- principal hormone responsible for lactation and proliferation/differentiation of breasts during pregnancy, function not known in males
- secretion is under tonic inhibitory control (always under check) by the hypothalamus via dopamine acting at D2 receptors
- major stimulus for secretion is suckling, possible stimulants also include TRH and oxytocin
- dopamine inhibits this
- not used clinically because high levels of this leads to infertility as it suppresses FSH/LH secretion in males and females
prolactin (PRL)
- high prolactin levels causes by prolactin secreting adenomas, hypothyroidism, dopaminergic antagonists (second generation antipsychotics that can cause infertility)
- characterized by amenorrhea (no menstrual cycle), galactorrhea (milk production from the breast unrelated to pregnancy or lactation), infertility in females
- characterized by loss of libido, gynecomastia (breast development) and infertility in males
- treatment options include transsphenoidal surgical resection/radiation therapy for adenomas or pharmacological (dopamine agonists bromocriptine and cabergoline as first line agents)
hyperprolactinemia
- MOA: inhibit prolactin release by stimulating dopamine D2 receptors in hypothalamus
- normalize serum prolactin levels, restore FSH/LH production, shrink tumor size
- clinical uses: hyperprolactinemia and acromegaly (acromegaly requires higher dose)
- adverse effects: nausea, headache, orthostatic hypertension
dopamine receptor agonists: bromocriptine (PARLODEL) and cabergoline (DOSTINEX)
two posterior pituitary hormones that are cyclic nonapeptides:
1. _____________: antidiuretic hormone for urinary water retention
2. _____________: controls uterine contraction and lactation
- because these two are similar in structure, if using one drug to treat problem with one you get effects on the other
vasopressin, oxytocin
- released by posterior pituitary in response to increased plasma osmolarity (thirst) or decreased blood volume (hypovolemia)
- possesses vasopressor and antidiuretic properties
- activates two types of G-protein coupled receptors (V1 receptors in blood vessels leading to vasopressor effect like constriction of blood vessels and V2 receptors in kidneys leading to antidiuretic effect like insertion of water channels)
vasopressin (ADH, PITRESSIN, AVP)
refers to inadequate ADH secretion, large volumes of dilute urine, thirst, dry mouth, excessive urination
diabetes insipidus
- a long acting vasopressin analog with minimal vasopressor activity and an antidiuretic to vasopressor activity 4,000 times that of vasopressin
- clinical uses: primary agent to treat diabetes insipidus (used IV, SC, intranasally, orally), decreases nocturnal urine production (used for nocturnal enuresis/bedwetting), releases von Willebrand factor and clotting factor VIII from vascular endothelium (used for treating various bleeding disorders)
- adverse effects: GI disturbances, HYPONATREMIA (low sodium in blood because sodium is diluted since kidney is retaining water), allergic reactions
desmopressin (DDAVP)
- ____________ is excessive ADH secretion (persistent stimulation of V1 and V2 receptors leading to hypertension and excessive water retention, this leads to dilution of extracellular Na+ leading to hyponatremia, coma, convulsions, death)
- causes: malignancy, CNS injury/disease, general surgery, medications (SSRIs, TCAs, haloperidol, sulfonylureas, Vinca alkaloids)
- treatment includes _____________ which is IV and blocks both V1 and V2 receptors and ______________ which is oral and is a selective V2 receptor antagonist, adverse effects of these are dry mouth, increased thirst, excessive urination, HYPERNATREMIA
syndrome of inappropriate ADH (SIADH), conivaptan (VAPRISOL), tolvaptan (SAMSCA)
- peptide hormone released from posterior pituitary gland
- stimuli for release: sensory stimuli from dilation of cervix during labor, stimulation of breast
- pharmacological/physiological effects: activates G-protein coupled receptors to contract uterine smooth muscle and myoepithelial cells in breast, input from cervix means uterine contractions (increased frequency and force), input from breast means milk letdown via contraction of myoepithelial cells (“milk letdown factor”, normal lactation can’t occur without oxytocin induced contraction)
- clinical uses:
1. for initiation and augmentation of labor (IV) - frequency and force of contractions is gestation dependent
2. to reduce or prevent post-partum hemorrhage (IM) - firm, contracted uterus less likely to bleed, given after delivery
3. to promote milk letdown (nasal spray) - relief of engorgement during inadequate breastfeeding, simple, safe, but usually only 50% effective
oxytocin
comprised of functional units called follicles which are single layers of epithelial cells arranged in a cavity with follicular lumen (where this stores hormones)
thyroid gland
cells that secrete thyroxine (T4) and triiodothyronine (T3)
follicular cells
cells that secrete calcitonin (which decreases plasma calcium levels)
parafollicular cells
- _______: released from the hypothalamus that stimulates the release of TSH from anterior pituitary
-_______: acts on receptors in thyroid follicle cells and stimulates the synthesis and release of T3 and T4 from thyroid - _______ and _______ inhibit both TSH and TRH synthesis and release by negative feedback regulation
TRH, TSH, T3, T4
inhibitors of TSH secretion other than T3 and T4 are ______ and _______
somatostatin and glucocorticoids/dopamine
small amounts of this are necessary for T3 and T4 synthesis but large amounts actually inhibit T3 and T4
iodide
________ belong to nuclear receptor family, exist as dimers with retinoid X receptors (RXR), within the cells T4 is converted to T3, T3 binds to these and activates transcription and protein synthesis of target genes, effects of these takes hours or days to manifest (latency)
thyroid hormone receptors/thyroid hormones
- all tissues: increase oxygen consumption, basal metabolic rate (BMR) and heat production
- heart: increase contractility, HR, cardiac output which leads to cardiac adverse effects
- nervous system: critical for optimal growth, development, and function
- liver: stimulate gluconeogenesis leading to hyperglycemia
- skeletal muscle: increase protein degradation and bone turnover leading to muscle and bone loss
- adipose tissue: stimulate lipolysis (increase fat metabolism) leading to weight loss
- OVERALL EFFECT IS CATABOLIC (breaks everything down)
pharmacological effects of thyroid hormones
_______ is more potent but less stable compared to _______ (thyroid hormones)
T3, T4
- myxedema (adults) due to autoimmune destruction of the thyroid
- Cretinism (congenital)
- secondary due to pituitary or hypothalamic disease (decrease TRH or TSH secretion)
hypothyroidism
- toxic goiter (Grave’s disease, antibodies stimulate thyroid)
- thyroid cancer
- inflammatory thyroid disease (thyroiditis)
- iodine-induced thyrotoxicosis (amiodarone)
hyperthyroidism
preferred and most widely used agent for thyroid replacement (pure form of T4) because of its stability, low cost, lack of antigenicity, and long half life (7 days which permits once daily dosing), T4 gets converted to T3 intracellularly so administration of T4 produces BOTH HORMONES
levothyroxine (T4) (SYNTHROID, LEVOXYL, LEVOTHROID)
3 to 4 times more potent than levothyroxine, faster onset but shorter duration of action, short half life means multiple daily doses so not recommended for routine replacement, disadvantages include higher incidence of cardiac adverse effects, higher cost, difficulty in monitoring, used in myxedema coma
liothyronine (T3) (CYTOMEL)
a mixture of T4 and T3 in 4:1 ratio to mimic the body composition of thyroid hormones, more potent than levothyroxine
liotrix (T4/T3) (THYROLAR)
porcine or bovine origin thyroid hormone replacement, disadvantages include protein antigenicity, product instability, variable hormone concentrations greatly limit their use in hypothyroidism
Armour Thyroid, Nature Thyroid
________ inducers like rifampin, phenytoin, phenobarbital, carbamazepine ________ clearance of T3 and T4 so patients on these require _______ doses of thyroid preparations due to increased clearance
CYP, increase, higher
- MOA: block iodide uptake by the gland through competitive inhibition of the iodide transport
- adverse effect: aplastic anemia so rarely used clinically (suppress bone marrow growth)
anion inhibitors: perchlorate (CIO4), pertechnetate (TcO4), thiocyanate (SCN0
- MOA: prevent hormone synthesis by inhibiting the thyroid peroxidase-catalyzed organification of tyrosine residues in thyroglobulin and coupling of iodotyrosine
- hormone synthesis but not the release is inhibited so clinical response takes 3-4 weeks since thyroid has large stores of T4)
- adverse effects: SKIN RASH, nausea, GI distress, agranulocytosis (rare but fatal), hypothyroidism
thioamides: methimazole (TAPAZOLE), PTU
which of the following (along with is MOA) inhibits peripheral conversion of T4 to T3 making it useful to treat thyroid storm, is preferable in pregnancy because it crosses the placenta less readily, and has risk of severe hepatitis that can be fatal so it’s reserved for first trimester of pregnancy and in thyroid storm?
- methimazole
- PTU
PTU
- MOA: high doses of this inhibit thyroid hormone synthesis, coupling, proteolysis, release
- clinical uses: effects occur rapidly within 2-7 days so useful in treating thyroid storm, decrease the size and vascularity of thyroid gland so used in preoperative preparation for thyroidectomy, CAUTION: effects are transient and reversible so these products should not be used as monotherapy
- adverse effects: iodism (acneiform rash, metallic taste, increased salivation, mucous membrane ulcerations)
iodides: Lugol’s solution (iodine and potassium iodide), Saturated potassium iodide solution (SSKI)
- MOA: beta and gamma emitter leads to follicular disruption and destruction of thyroid gland within few weeks after oral administration WITHOUT pain, destroys cancerous and normal thyroid cells (doesn’t discriminate)
- adverse effects: hypothyroidism, worsening of ophthalmopathy, contraindications are pregnancy and lactation because it’s a radioactive isotope
radioactive iodine
- MOA: block beta-1 adrenergic receptors in the heart –> decrease HR and contractility (which is increased in hyperthyroidism), not an anti-thyroid medication necessarily
- clinical use: adjunct therapy to treat symptoms of hyperthyroidism like tachycardia, arrhythmia, hypertension especially in thyroid storm
- adverse effects: bradycardia, AV block, hypotension, bronchospasm in asthmatics
beta-blocker: propranolol
which part of the adrenal gland secretes adrenal steroids like aldosterone, cortisol, DHEA?
cortex
which part of the adrenal gland secretes catecholamines like epinephrine and norepinephrine?
medulla
what is a precursor to several hormones?
cholesterol
rate limiting step regulated by ACTH in conversion of cholesterol to aldosterone and cortisol
cholesterol to pregnenolone
adrenal corticosteroids that regulate glucose metabolism (protein and lipid metabolism) and suppress immune function for anti-inflammatory and immunosuppressive effects (more important clinically)
glucocorticoids (cortisol)
adrenal corticosteroids that regulate water and electrolyte balance (promotes Na+ and water retention causing an increase in BP, promotes K+ excretion causing hypokalemia
mineralocorticoids (aldosterone)