53 Questions
What distinguishes the endocrine system from other physiological systems?
It uses soluble factors known as hormones
Which type of hormones are the most numerous in the body?
Peptides
How does the diversity of hormones change as one moves from simple to higher life forms?
Increases
What are the mediators of control mechanisms in endocrine physiology?
Hormones
What influences the ultimate biologic activity and/or stability of mature hormones?
Glycosylation
How are many hormones secreted?
Via exocytosis of stored granules
What regulates the secretion of continually released hormones like steroids?
Kinetic influences on synthetic enzymes or carrier proteins
What protein plays a role in trafficking cholesterol for steroid biosynthesis?
Steroidogenic acute regulatory protein (StAR)
What influences the circulating levels of hormones in addition to the rate of secretion and its nature?
Rates of hormone degradation and/or uptake
What is one of the important functions of plasma carriers for specific hormones?
Providing a hormonal reserve
How do plasma carriers help in smoothing fluctuations in hormonal levels over time?
By serving as a reservoir of inactive hormone
Why are plasma carriers considered vital in modulating levels of free hormones?
To prevent fluctuations in hormonal levels
What type of hormones are mostly bound to large proteins called steroid binding proteins (SBP)?
Steroid hormones
What is the main function of sex hormone-binding globulin (SHBG)?
Binding to steroid hormones
Why are only small amounts of free hormone dissolved in the plasma?
Due to the hydrophobic nature of steroid hormones
What happens when the equilibrium between SBP-hormone complex and free hormone changes?
Free hormone is released and diffuses across cell membranes
What distinguishes the endocrine system from other physiological systems?
It uses soluble factors known as hormones
Why do the number of hormones and their diversity increase as one moves from simple to higher life forms?
Reflecting the added challenges in providing for homeostasis in more complex organisms
Which type of hormones are by far the most numerous?
Peptide hormones
What is the main evolutionary trend seen in hormones as organisms become more complex?
Increase in the diversity of hormones
Which factor influences the circulating half-life of a hormone and has therapeutic implications for hormone replacement therapy?
Rates of hormone degradation and/or uptake
What is one of the important physiologic functions of plasma carriers for specific hormones?
Preventing fluctuations in hormonal levels
How do plasma carriers help restrict the access of hormones to some sites?
By preventing the degradation and uptake of bound hormones
What is a key function of plasma carriers in modulating levels of free hormones?
Regulating the levels of free hormones
Which class of hormones predominantly exerts their actions via nuclear receptors?
Hydrophobic hormones
Which hormone regulates plasma volume by affecting serum electrolytes?
Vasopressin
What is the primary action of mineralocorticoids in the body?
Regulating plasma volume via electrolytes
How do hydrophilic hormones typically exert their acute effects?
By binding to cell surface receptors
How can the availability of hormones that bind to carrier proteins, like steroids, be regulated?
By regulating the expression and secretion of the carrier proteins
In a pathophysiologic scenario, what effect can certain medications have on hormone levels?
Alter levels of binding proteins or displace bound hormones
Why is the temporal window for hormone action limited in some cases?
As a result of passage through the liver or pulmonary circulation
What role do free hormones play in the feedback and control mechanisms within the endocrine system?
They are needed for feedback and control of hormone synthesis and secretion
Peptide hormones are distinguished by their ability to diffuse freely through the cell membrane.
False
Steroids and thyroid hormones primarily act on nuclear receptors located in the cytoplasm.
True
Hormone receptors needed to evolve in order to allow for spreading of hormone actions.
True
The distinctive β-chains of TSH, FSH, and LH arose from a common ancestral gene through divergent evolution.
False
Pulsatile secretion of hormones is primarily triggered by the activity of oscillators in the pituitary gland.
False
Hormones secreted in a pulsatile manner carry the same information to target tissues as hormones exposed to a constant concentration.
False
Pulsatile secretion of hormones presents challenges for hormone replacement therapy when a hormone needs to be replaced due to excess secretion.
False
The main function of pulsatile secretion is to ensure a constant and steady supply of hormones to the body's target tissues.
False
Steroid hormones are soluble in plasma and can freely access the extravascular compartment.
False
Catecholamine and most peptide hormones are transported in a bound form by steroid binding proteins (SBP).
False
Sex hormone–binding globulin (SHBG) primarily binds to cortisol and corticosteroids.
False
Only the SBP-hormone complex is able to diffuse across cell membranes.
False
Thyroid hormone predominantly acts on nuclear receptors.
False
Insulin is a hydrophobic hormone that binds to cell surface receptors.
False
Cortisol regulates plasma volume via effects on serum electrolytes.
False
Parathyroid hormone controls basal metabolism in most tissues.
False
What is a critical mechanism for regulating the bioavailability of thyroid hormones?
Regulating the expression and secretion of carrier proteins
How can medications in a pathophysiologic setting affect hormone levels?
By altering levels of binding proteins
What is a key factor that influences the temporal window for hormone action?
Destruction of hormones by the pulmonary circulation or liver
How do hormones primarily bring about changes in ion channel activity?
By binding to receptors on the cell membrane
What is the ultimate purpose of the action of hormones on target cells?
To promote growth in target cells
Test your knowledge on the factors influencing circulating levels of hormones such as degradation, uptake, receptor binding, and affinity for plasma carriers. Explore how stability impacts the half-life of hormones and its therapeutic implications.
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