• Endocrine, nervous and immune systems work together to regulate responses to internal
and external environment
• Hormone release is regulated
... [Show More] by:
o Chemical factors (BGL, Ca levels)
o Endocrine factors (cortisol)
o Neural control- ANS stimulates
• Negative feedback- MOST COMMON, occurs when a changing chemical, neural or
endocrine response DECREASES synthesis and secretion of hormone
• Positive feedback occurs when a neural, chemical, or endocrine response INCREASES
synthesis and secretion of hormone.
o Also occurs when increased hormone level further increases synthesis and
secretion of that same hormone
o Ex- cyclic rise of estradiol levels
• Hormone receptors of target cells have 2 functions
o Recognize and bind with high affinity to their particular hormones
o Initiate signal to appropriate intracellular effectors
o The sensitivity or affinity of the target cell to a particular hormone is r/t the
concentration of receptors for cell- more receptors= more sensitive to stimulating
effects of hormone
• High concentrations of hormone decrease the number or affinity of receptors per cell=
DOWNREGULATION
o The cell can adjust its sensitivity to the concentration of signaling hormone
o Receptors on plasma membrane are continuously synthesized and degraded so
changes in receptor concentration may occur within hours
Thyrotoxicosis
• Condition that results from any cause of an increased amt of TH levels
• HYPERthyroidsm= form of thyrotoxicosis which excess amts of TH are secreted
• Thyrotoxicosis and hyperthyroidism used interchangeably
• More prevalent in women and iodine-deficient geographical areas
• Diseases that cause primary hyperthyroidism= Graves’ disease, toxic multinodular goiter,
toxic adenoma
• Secondary- less common and caused by TSH-secreting pituitary adenomas
• S/S are attributable to metabolic effects of increased circulating levels of TH
o Increased metabolic rate with heat INTOLERANCE
o Thin hair, exophthalmos, normal or enlarged thyroid (goiter), tachycardia (HF),
wt loss, diarrhea, N/V, warm skin, sweaty palms, hyperreflexia, pretibial
myxedema, restlessness, insomnia, fatigue, tremor
• Treatment= antithyroid drug therapy, radioactive iodine, surgery. Major complication of
hyperthyroidism tx= hypothyroidism [Show Less]