Hypothalamic, Adrenal, Pituitary, Thyroid, Adrenal, Hypothalamus, Pituitary Flashcards
What is the overall function of the endocrine system? How would you define the endocrine system?
Function: processes involved in maintaining physiological equilibrium (homeostasis)
-tissues or glands that secrete hormones into blood –> bind to specific receptors that allows the hormone to exert effect
–> only affect tissues with appropriate receptor
-negative feedback system regulates most hormone secretion
How is the endocrine system diff than the NS?
–> NS: neurotransmitters, neurohormone
–> endocrine: hormones
- What is meant by the lock & key relationship? How does that “relationship” influence hormone delivery and action throughout the body?
-tissues or glands that secrete hormones into blood –> bind to specific receptors that allows the hormone to exert effect
–> only affect tissues with appropriate receptor
What is set point?
In endocrinology, a set point is the physiological value around which a normal range fluctuates. For example, body weight and body temperature are set points that the endocrine system contributes to regulating. A set point is also the level at which a physiological state tends to stabilize, such as body temperature or weight.
What is a negative feedback loop?
-way the system maintains homeostasis
-secretion of specific hormones are turned on or off by specific physiological changes
EX: plasma glucose levels and insulin/glucagon response
Difference between steroid and non-steroid hormones and delivery to target tissues/organs/mech of action
A steroid hormone will actually enter the target cell and act directly on the DNA of the cell. A non-steroid hormone will land on a receptor on the cell surface, but not enter the cell. In this case a second messenger will carry out the work, but the hormone stays outside the cell.
How does the hypothalamus influence the Ant Pituitary?
Hypothalamus: major link between nervous and endocrine systems
-pituitary gland attached to hypothalamus by infundibulum
FUNCTIONS OF HYPOTHALAMUS:
-synthesizes and secretes regulatory hormones: releasing hormones (stimulate anterior pituitary hormone release) and release inhibitory hormones (inhibit release of anterior pit. hormones)
-directs pituitary gland (hypophysis)
-regulatory hormones need to travel through hypophyseal portal system to reach ant. pit.
GnRH–> FSH, And, LH
GHRH–> growth hormone
Somatostatin (GHIH)–> inhibits GH release
TRH–> TSH and prolactin
Dopamine–> inhibits prolactin release
CRH–> ACTH
PRH–> prolactin
Hypothalamus and posterior pituitary:
-synthesizes two hormones stored in post. pit.
–> oxytocin and vasopressin (ADH)
VASOPRESSION;
-regulates blood volume and salt concentration (plasma osmolality)
-the cells of the supraoptic and paraventricular nuclei are osmoreceptors
-released by post pit in response to low blood volume (baroreceptors sense low BP)
-increased plasma osmotic pressure (osmoreceptors in hypothalamus sense increased solute in blood)
-alcohol is a diuretic–> less ADH is produced–> less water retention
Pituitary disorders:
IN GENERAL:
-too much or too little hormone release
-hyperpituitarism
–>acromegaly/gigantism (inc. GH)
–> Cushing’s disease (inc. cortisol)
-hypopituitarism
–> Diabetes insipidus (decreased ADH)
COMMON SYMPTOMS:
-headache
-visual changes
-lethargy/fatigue
-nausea and vomiting
-nasal drainage
-behavior changes
-changes in sense of smell
TUMORS:
-pituitary tumors account for 10-15% of intra-cranial tumors
-majority are adenomas: benign
Gigantism vs Acromegaly
From anterior pituitary
GIGANTISM
- excessive
secretion of GH in
children
-epiphyseal plate not yet closed
ACROMEGALY
-GH secretion excessive in adults
-most often in 4th decade
-slow but continuous progression
Cortisol release and functions
-normally controlled by hypothalamus
–> CRH
-CRH triggers ant pit ot secrete ACTH into vascular system–> ACTH is carried in the blood to the adrenal cortex, stimulating the synthesis of cortisol
FUNCTIONS:
-counter regulatory to insulin: promotes hyperglycemia
-decreases bone formation (decrease osteoblast function) and decreases intestinal Ca++ absorption
-acts as a diuretic
-influences immune function (inhibits production/release of inflammatory mediators)
Cushing’s disease etiology
-associated with the adrenal and pituitary glands
-hypersecretion of cortisol
CAUSES:
(Pituitary cushing’s)
-pituitary adenoma- secretees ACTH
-ACTH dependent = disease
(Adrenal cushing’s)
-adrenal adenoma- secretes cortisol
–> exogenous corticosteroids (iatrogenic cushing’s syndrome)
-ACTH-indepedent- Syndrome
Cushing’s disease S/S
INCREASED CORTISOL
-central obesity
–> rapid weight gain with sparing of limbs
–> moon face and buffalo hump fat distribution
-skin
–> thinning and capillary fragility
–> bruising
–> striae
–> poor wound healing
-muscle wasting and weakness
-tachycardia; hypertension
-osteoporosis
–> impaired GI ca++ absorption (antagonizes vit D)
-hyperglycemia/DM (stress response)
-immunosuppression–> increased infection risk
Cushing’s disease similarities with DM
-hyperglycemia
-immunosuppression
-poor wound healing
-hypertension
Cushing’s disease medical treatment (steroids)
–>DISEASE: pituitary tumor excision via trans-sphenoidal surgery
–> SYNDROME: adrenal tumor excision- adrenalectomy
-Iatrogenic: decrease corticosteroids dosing
What is the primary function of the thyroid gland?
Thyroid follicles produces T3 and T4
-T4 to T3 ratio is 15 to 1
-T4 is a pro-hormone that is converted to the active T3
PRIMARY FUNCTIONS:
-growth and development
-increased catecholamine effect
-increased BMR
-important for brain and muscular development
-CV: increased HR/contractility and cardiac output
-CNS: increased arousal rates
Hyperthyroidism S/S
EXCESSIVE SECRETION OF:
-thyroxine (T4) and/or triiodithyronine (T3)
S/S:
-unintended weight loss and diarrhea
-anxiety and nervousness and tremors
-heat intolerance
-fatigue/muscle weakness
-palpitations/tachycardia/afib /hypertension
-hyperglycemia
-osteopenia (long term)
Hypothyroidism S/S
-lethargy
-fatigue
-bradycardia
-edema
-weight gain
-cold intolerance
-dry skin/brittle hair and fingernails
-goiter
Differences between T3 and T4
T3
-active form of T4
-iodine is necessary for formation of T4 and T3
-T4 converted to T3 which is active
T4
-much more abundant than T3
-considered a pro-hormone
-not active
Hyperthyroidism medical treatment:
-radioiodine therapy- often leads to hypothyroidism
MEDS:
-thyrostatics:
–> inhibit iodination of thyroglobulin (inhibit T3 and T4 production)
–> inhibit conversion of T4 to T3
-beta blockers
-thyroid surgery: thyroidectomy- not very common because medical therapy is effective
Steps of thyroid hormone release-HPA axis:
TRH from hypothalamus to pituitary
TSH from pituitary to thyroid gland
Thyroid gland releases T3 and T4 –> target tissues: heart, liver, bone, CNS
Function of iodine for thyroid
required for production of thyroid hormones
Graves Disease S/S; which gland/hormones are involved?
(type of hyperthyroidism- excessive T3 or T4)
-autoimmune disease: thyroid autoantibodies activate the TSH-receptor (pituitary) –> increase in thyroid hormone
-can also be caused by a pituitary tumor
SYMPTOM:
-Graves’ opthalmopathy (exopthalmos/proptosis)
—>bulging of eye anteriorly
—>Thyroid Eye Disease (due to inflammation)
Relationship between parathyroid hormone and OP
PTH FUNCTION:
-regulates serum calcium
-increases blood calcium concentration when it is too low (hypocalcemia) by stimulating osteoclasts to release more ca from bone
-decreases secretion of Ca by kidney
-activates vitamin D, which stimulates uptake of Ca from the intestine (diet)
-** opposite effect as calcitonin which is produced by thyroid gland (lowers blood Ca levels)
