Chapter 5: The Endocrine System Flashcards
Insulin
Pancreas produced peptide hormone that induces the transport of glucose into organs and the storage of excess glucose when blood glucose concentrations are high. Released by beta cells of the endocrine system of the pancreas.
Glucagon
Pancreas produced peptide hormone that triggers the release of sugar stores which raises blood glucose concentration. Glucagon triggers gluconeogenesis (process of harvesting glucose from non carbohydrate sources such as lactate, AA, and glycerol)
Diabetes mellitus (type one and two)
Type I: Auto immune disease in which insulin producing cells in the islets of Langerhans are destroyed.
Type II: caused by end organ insensitivity to insulin.
Glands
Organs in the endocrine system that secrete hormones.
Hormones
Signaling molecules that are secreted directly into the bloodstream to distant target tissues. Hormones bind to receptors, inducing a change in gene expression or cellular functioning.
Classification of hormones by chemical structure/identity (three kinds)
Peptide hormones
Steroid hormones
Amino acid derivative hormones
Peptide hormones
Hormones that are made up of amino acids.
Peptide hormones contain a charge and are therefore polar and water soluble.
Derived from precursor polypeptides and transported to the Golgi apparatus for further modification that activate the hormones and direct them to the correct location in the cell.
First and second messenger
The peptide hormone is considered the first messenger.
After the peptide hormone binds to the receptor and triggers the transmission of a second signal, known as the second messenger.
Because peptide hormones are charged and cannot pass through the plasma membrane, they must bind to an extra cellular receptor.
Signaling cascade
The connection between the hormone at the surface and the effect brought about by second messengers.
Signal amplification
An increase in signal intensity. One hormone molecule may bind to multiple receptors before it is degraded, and each receptor may activate multiple enzymes, each of which will trigger the production of large quantities of second messengers.
Three types of common second messengers
Cyclic adenosine monophosphate (cAMP)
Inositol triphosphate (IP3)
Calcium
G-protein coupled receptor
Integral membrane proteins that form the fourth largest superfamily in the human genome. G protein coupled receptors mediate most cellular responses to hormones and neurotransmitters.
Activation of a G protein-coupled receptor example
The binding of a peptide hormone triggers the receptor to either activate or inhibit an enzyme, called adenylate cyclase, raising or lowering the levels of cAMP (cyclic adenosine monophosphate) accordingly. cAMP combined to intacellular targets, such as protein kinase A, which phosphorylates transcription factors like cAMP Response element – binding protein (CREB) to exert the hormones ultimate effect of expressing a gene.
Transient (medical term)
Temporary
Steroid hormones
Derived from cholesterol and are produced primarily by the gonads and adrenal cortex.
Nonpolar molecules that can easily cross the cell membrane.
Receptors are usually intracellular or intranuclear. The steroid hormone – receptor complexes bind directly to DNA resulting in either increased or decreased transcription of particular genes.
Dimerization
Pairing of two receptor – hormone complexes.
Dimer means two parts
Steroid carriers
Steroid hormones are nonpolar, and therefore must be carried by proteins in the bloodstream to travel around the body. Some carriers are very specific and carry only one hormone (such as sex hormone binding globulin), while other protein carriers are non-specific (such as albumin).
Key concept regarding action of peptide and steroid hormones.
Peptide hormones have surface receptors and act via a second messenger systems.
Steroid hormones bind to intracellular receptors and function by binding to DNA to alter gene transcription.
Key concept and mnemonic for onset and duration of peptide and steroid hormones.
Insulin is a peptide hormone, and it has to be released at every meal in order to be active. Thus, it has fast onset but is short acting (like most peptide hormones).
Estrogen and testosterone are steroid hormones that promote sexual maturation. This is a slower, but longer lasting change (as is true for most steroid hormones).
Thyroxine-binding globulin (TBG) as an example of levels of carrier proteins changing the levels of active hormones.
Hormones are generally inactive while attached to a carrier protein and must dissociate from the carrier to function. Some conditions increase the quantity of a protein that carries thyroid hormones, such as TBG. This causes the body to perceive a lower level of thyroid hormone because the increased quantity of TBG binds a larger proportion of the hormone, meaning there is less free hormone available.
Real world example of thyroxine-binding globulin (TBG) causing increased levels of thyroid hormones in pregnancy.
During pregnancy, high levels of estrogen and progesterone cause increased production of TBG. In order to compensate, people who are pregnant secrete much higher levels of thyroid hormones. Thus, in order to diagnose thyroid disease during pregnancy, different reference values must be used.
Amino acid – derivative hormones
Derived from one or two amino acids, usually with a few additional modification.
Less common than peptide and steroid hormones, but include some of the most important hormones.
Four amino acid derivative hormones, their source, and actions.
Epinephrine and Norepinephrine (the catecholamines), source from the adrenal medulla, causes increase blood glucose concentrations and increase heart rate, dilate bronchi, alter blood flow patterns. Extremely fast onset but are short-lived like peptide hormones. Think adrenaline rush.
Triiodothyronine (T3) and Thyroxine (T4), source from the thyroid (follicular cells), stimulate metabolic activity, Slow onset but long duration like a steroid hormone. They regulate metabolic rate over long period of time.
A way to decipher peptide, amino acid-derivative, and steroid derivative hormones.
In general, most peptide and amino acid derivative hormones have names that end in -IN or -INE (insulin, vasopressIN, thyroxINE, triiodothyronINE, etc.)
In general, most steroid hormones have names that end in -ONE, -OL, or -OID (testosterONE, aldosterONE, cortisOL, aldosterONE, estradiOL, and other mineralcorticOIDS, etc.)
Nonexhaustive, but may help for test day.
Classification of hormones by target tissue (two types)
Direct hormones and tropic hormones
Direct hormones
Secreted and then act directly on a target tissue.
For example, insulin released by the pancreas causes increased uptake of glucose by muscles.
Tropic hormones
Require an intermediary to act. Usually originate in the brain and anterior pituitary gland, allowing for the coordination of multiple processes within the body.
For example, gonadotropin releasing hormone (GnRH from chapter 2) from the hypothalamus stimulates the release of luteinizing hormone (LH) and follicle – stimulating hormone (FSH). LH then act on the gonads to stimulate testosterone production in males and estrogen production in females. GnRH and LH do not cause direct changes in the physiology of muscle, bone, and hair follicles; rather they stimulate the production of another hormone by another endocrine gland that acts on these target tissues.
Endocrine organs
Hypothalamus, pituitary, thyroid, parathyroid glands, adrenal glands, pancreas, gonads, pineal gland. Called endocrine organs because hormone production is their main function.
Hypothalamus
The bridge between the nervous and endocrine system.
The release of hormones by the hypothalamus is regulated by NEGATIVE FEEDBACK. When hormone levels reach a certain level, the hypothalamus and pituitary gland reduce the production of hormones to maintain a balance.
Example: When thyroid hormone levels are high, the hypothalamus and pituitary gland reduce the production of thyroid-stimulating hormone (TSH) and thyrotropin-releasing hormone (TRH)
Nuclei in the three sections of the hypothalamus
Lateral
Ventromedial
Anterior
These nuclei play roles in emotional experience, aggressive behavior, sexual behavior, metabolism, temperature, regulation, and water balance.
Hypothalamus (deeper)
Regulates the anterior pituitary through tropic hormones, and through direct neural connection to the posterior pituitary, capable of having organism wide effects. Located in the forebrain, directly above the pituitary gland and below the thalamus. Because of the close proximity between the hypothalamus and the pituitary gland, the hypothalamus controls the pituitary through peregrine release of hormones.
Among other things, it receives some of the light input from the retina helps to control sleep-wake cycles and also responds to increases in blood osmolarity (concentration of solutes in blood).
Negative feedback regarding the hypothalamus
The release of hormones by the hypothalamus is regulated by negative feedback (occurs when a hormone, or product, later in the pathway inhibits hormones, or enzymes, earlier in the pathway). This type of feedback maintains homeostasis and conserve energy by restricting production of substances that are already present and sufficient quantities.
Hypophyseal portal system
Blood vessel system that is a direct inextricable link between the hypothalamus and the anterior pituitary. Note: the posterior pituitary does not receive tropic hormones through the hypophyseal portal system.
Thus, hormones released from the hypothalamus travel directly to the interior pituitary and cannot be found in appreciable concentrations in the systemic circulation.
Hypophysis
Alternative term for the pituitary
Some (four) tropic hormones released by the hypothalamus and the hormone released by the anterior pituitary in response:
GnRH - FSH and LH
Growth hormone-releasing hormone (GHRH) - Growth hormone (GH)
Thyroid releasing hormone (TRH) - thyroid stimulating hormone (TSH)
Corticotropin-releasing factor - adrenocorticotropic hormone (ACTH)
All of the hormones from the hypothalamus cause an increase in hormonal response from the anterior pituitary, except for one: dopamine (PIF, prolactin inhibiting factor). Dopamine inhibits release of prolactin from the anterior pituitary.
-tropic suffix
Turned to, or attracted to
One exception to the pattern of increased hormonal reaction of the anterior pituitary from the hypothalamus
Prolactin – inhibiting factor (PIF), which is actually dopamine, is released by the hypothalamus and causes a DECREASE in prolactin secretion. It is the absence of PIF that allows prolactin to be released.
Negative feedback effects of the hypothalamus and anterior pituitary: corticotropin-releasing factor (CRF), adrenocorticotropic hormone (ACTH), and cortisol EXAMPLE Also, what is cortisol and what does it do?
Release of CRF from the hypothalamus will stimulate the anterior pituitary to secrete ACTH. ACTH will then cause the adrenal cortex to increase the level of cortisol being secreted into the blood. Cortisol is detrimental when levels become too high. Cortisol inhibits the hypothalamus and interior pituitary from releasing CRF and ACTH.
CRF and ACTH goal is getting more cortisol in the blood. Since cortisol receptors are present in the hypothalamus and pituitary, they recognize the presence of cortisol and therefore discontinue production of CRF and ACTH.
Cortisol is released in response to stress. It increases sugar in the blood by converting proteins into glucose (gluconeogenesis). Also reduces inflammation, maintains blood pressure, helps control sleep wake cycles.
Relationship between the hypothalamus and the posterior pituitary
Neurons in the hypothalamus send their axons down the pituitary stock directly into the posterior pituitary, which can then release oxytocin and anti-diuretic hormone.
Note: The posterior pituitary does not receive trophic hormones through the hypophysial portal system. The hypophyseal portal system is strictly between the hypothalamus and the anterior pituitary.
Oxytocin
Stimulates uterine contractions during labor, as well as milk letdown during lactation. May also be involved in bonding behavior. Released by posterior pituitary.
Oxytocin is unusual in that it has a positive feedback loop: the release of oxytocin promotes uterine contraction, which promotes more oxytocin release, which promotes stronger uterine contractions, and so on.
Antidiuretic hormone (ADH or vasopressin)
Increases reabsorption of water in the collecting ducts of the kidneys. ADH (or vasopressin) is secreted in response to increased plasma osmolarity (increased solute concentrations within the blood).
Note: hypothalamus detects increased plasma osmolarity, synthesizes ADH, sends a direct signal to posterior pituitary, ADH is secreted by posterior pituitary and increases reabsorption of water in the kidneys by increasing the permeability of the collecting duct.
Remember: the posterior pituitary does not make hormones.
Pituitary tumor, release of prolactin
A tumor in the pituitary gland may result in compression of the portal system that connects to the hypothalamus. This may block the ability of prolactin-inhibiting factor (PIF or dopamine) from reaching the anterior pituitary and exerting its effects. Thus more prolactin will be released, resulting in lactation. Milk production in a male or non-pregnant female should lead a physician to suspect the presence of a pituitary tumor. Interesting example.
Two divisions of the pituitary gland
Anterior and posterior pituitary
Products of the anterior pituitary FLAT PEG
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Adrenocorticotropic hormone (ACTH)
Thyroid-stimulating hormone (TSH)
Prolactin (dopamine)
Endorphins
Growth hormone (GH)
FLAT are all tropic
PEG are all direct
What is Cortisol, regarding blood sugar, and where it is produced and secreted?
Cortisol helps maintain blood sugar levels by converting protein and fat into glucose (gluconeogenesis) and working as an antagonist of insulin. Increases sugar in the bloodstream (gluconeogenesis, cortisol also decreases glycogenesis (glycogen synthesis)) Cortisol is made by the adrenal cortex.
Hypothalamus (corticotropic releasing hormone CRH), anterior pituitary (adrenocorticotropic hormone ACTH, adrenal cortex (cortisol)
Suprachiasmatic nucleus
Part of the hypothalamus that receives some light input from the retinae and helps control sleep-wake cycles.
Remember that that chiasma is a part of the brain where the optic nerves cross.
Tropic hormones
Work by causing the release of another hormone at the organ level
Pathologic
Indicative of or caused by disease
Adrenocorticotropic. Break down the meaning.
Adreno and cortico tell us where the message is going. The cortex of the adrenaline gland. Tropic means it’s attracted to. So, the adrenocorticotropic (ACTH) is a hormone released from the anterior pituitary and heads to the adrenal cortex (which is stimulated by release of the corticotropic releasing factor (CRF) from the hypothalamus). Great example of a tropic hormone.
Prolactin as a direct hormone, what it does and why it is an unusual hormone.
Anterior pituitary, remember FLAT PEG
Increases milk production, secreted by the anterior pituitary. It is unusual hormone because the release of prolactin inhibiting factor (PIF, or dopamine) release from the hypothalamus DECREASES prolactin secretion. In pregnancy, levels of estrogen and progesterone and dopamine are high which allow for development of milk ducts, but it isn’t until after the expulsion of the placenta, when dopamine (et al) levels drop that milk is produced.
The presence of PIF (dopamine) prevents lactation. The presence of prolactin produces milk.
Milk ejection (hypothalamus, posterior pituitary and anterior pituitary)
Nipple stimulation activates hypothalamus following two different reactions.
First, Posterior pituitary releases oxytocin, resulting in contracting of smooth muscle in breast.
Second, hypothalamus stops releasing dopamine (PIF) into the anterior pituitary, increasing prolactin, causing milk production.
Recalling that it is the presence of dopamine that prohibits prolactin and thus lactation. This is uncommon regarding feedback of hormones from the hypothalamus.
Endorphins
Anterior pituitary, remember FLAT PEG.
Decrease perception of pain.
Hypothalamus (corticotropic releasing hormone CRH) signals anterior pituitary to release endorphins.
Interesting, the adrenal medulla releases catecholamines (epinephrine and norepinephrine) in response to CRH.
Growth hormone (GH)
Anterior pituitary. Remember FLAT PEG
Promotes growth of bone and muscle. GH prevents glucose uptake in certain tissues (those that are not growing) and stimulate breakdown of fatty acid. This increases the availability of glucose overall, allowing bone and muscle to use it. Released by growth hormone-releasing hormone (GHGH) from hypothalamus.
Bone growth originates in the epiphyseal plates.
Epiphyseal plates
Growth plates where bone growth originates.
Acromegaly
Adult gigantism. Anterior pituitary continues to produce GH into adulthood and the smaller bones in the body continue to grow. Causes enlargement of the face, hands, and feet.
Gigantism and dwarfism
Excess, or deficit, of GH in childhood before closure of the epiphyseal plates.
Due to over expression or under expression of GHRH. May be caused by pituitary tumor that secretes excess GH directly, rather than an ectopic GHRH-producing tumor.
An ectopic tumor is a tumor that develops outside of its usual location, and produces hormones or other substances that are not normally produced in that area. Lungs, pancreas, adrenal glands, thyroid gland, thymus, etc.
Posterior pituitary
Contains the nerve terminals of neurons with cell bodies in the hypothalamus. Receives and stores two hormones produced by the hypothalamus: oxytocin and antidiuretic hormone (ADH).
Key concept: the two hormones released from the posterior pituitary, ADH and oxytocin, are actually synthesized in the hypothalamus and released by the posterior pituitary. THE POSTERIOR PITUITARY DOES NOT SYNTHESIZE ANY HORMONES.
Thyroid
Controlled by the thyroid-stimulating hormone from the anterior pituitary. Located on the front surface of the trachea, located by palpating near the base of the neck. Moves up and down with swallowing.
Two major functions of the thyroid
Setting basal metabolic rate
Promoting calcium homeostasis
Triiodothyronine (T3) and thyroxine (T4)
Produced by iodination of tyrosine (an amino acid) in the follicular cells of the thyroid. These hormones reset the basal metabolic rate by making energy production more or less efficient, as well as altering the utilization of glucose and fatty acids.
Increase in triiodothyronine (T3) and thyroxine (T4) leads to increase in cellular respiration. Negative feedback loop: high levels of T3 and T4 leads to decreased synthesis of triiodothyronine and thyroxine, prevents excessive secretion of triiodothyronine and thyroxine.
Hypothyroidism
A condition where thyroid hormones are secreted in insufficient amounts or not at all caused by deficiency of iodine (need iodine to synthesize tyrosine into triiodothyronine (T3) and thyroxine (T4)).
Characterized by lethargy, decreased body temperature, slower respiratory and heart rate, cold intolerance, and weight gain.
Cretinism
Intellectual disability and developmental delay. Most children are tested at birth for appropriate levels of triiodothyronine and thyroxine as low levels can cause cretinism.
Hyperthyroidism
Caused by excessive thyroid hormones. Opposite symptoms of hypothyroidism: heightened activity levels, increased body temperature, increased respiratory and heart rate, heat intolerance, and weight loss.
Calcitonin mnemonic
CalciTONin “TONes down” calcium levels in the blood.
Calcitonin is made in C-cells (parafollicular cells) of the thyroid. Calcitonin helps regulate the levels of calcium in the blood, helps control the building and breakdown of bone.
C cells (parafollicular cells)
Cell type in thyroid that produce calcitonin.
(C cells — Calcitonin; calcitonin reduces calcium levels in the blood)
Two types of cells in the thyroid
Follicular cells: produce thyroid hormones
C-cells (parafollicular cells): produce calcitonin
Three ways that calcitonin decrease plasma levels of calcium
Increasing calcium excretion from kidneys
Decrease calcium absorption by gut
Increase calcium storage in bone
Calcium functions
Bone structure and strength
Release of neurotransmitter from neurons
Regulation of muscle contraction
Clotting of blood (calcium is a cofactor)
Cofactor
A non-protein chemical compound or metallic ion that helps enzymes catalyze biochemical reactions.
Parathyroid glands
Four small pea-sized structures that sit on the posterior surface of the thyroid. Releases parathyroid hormone (PTH).
Parathyroid hormone (PTH)
ANTAGONIST OF CALCITONIN (calcitonin is made in the thyroid, so think that parathyroid hormone antagonizes the thyroid), raises blood calcium levels. Also promotes phosphorus homeostasis. Activates vitamin D (required for absorption of calcium and phosphorus in the gut).
Decreases excretion of calcium by the kidneys.
Increases absorption of calcium in the gut
Increases bone resorption
Calcium and phosphorus homeostasis
Calcitonin
Parathyroid hormone (PTH)
Adrenal glands
Located on top of the kidneys. Adrenal means near or next to the kidneys. Each gland consists of a cortex and medulla.
Adrenal cortex
Secretes corticosteroids.
Glucocorticoids such as cortisol which helps regulate glucose metabolism by increasing gluconeogenesis and decreases glycogenesis.
Mineralocorticoids such as aldosterone that increases blood pressure via a pathway known as the renin-angiotensin-aldosterone pathway. Makes ya thirsty.
Sex hormones like androgen and estrogen.
Three types of corticosteroids
Glucocorticoids
Mineralcorticoids
Cortical sex hormones
Glucocorticoids
Steroid hormones that regulate glucose levels and impact protein metabolism.
Glucocorticoids are produced in the adrenal cortex and released by the cortex of the adrenal glands.
Cortisone is a glucocorticoid
Two main types of glucocorticoids and their function
Cortisol: increases gluconeogenesis (produces glucose from non carbohydrate sources) and decrease glycogen synthesis. Recall that glycogen is a stored form of glucose. CORTISOL IS AN INSULIN ANTAGONIST.
Cortisone: decreases inflammation and immunological responses.
Glucocorticoid release (organs and hormones involved)
Corticotropin-releasing factor (CRF)
from hypothalamus.
Adrenocorticotropic hormone (ACTH) from the anterior pituitary.
Glucocorticoids (sugar, salt, sex) from the adrenal cortex.
Mineralocorticoids
Used in salt and water, most profound effects are on the kidneys.
Most noteworthy mineralocorticoids is ALDOSTERONE.
Aldosterone
A mineralocorticoid steroid that increases sodium and potassium reabsorption in the distal convoluted tubule and collecting duct of the nephron, ie increases blood pressure when stretch detectors sense a drop in blood pressure. This does not change the plasma osmolarity because water and sodium cations flow together.
Note: contrast to antidiuretic hormone which only increases water reabsorption which decreases plasma osmolarity.
Renin-angiotensin-aldosterone system
Controls aldosterone in the body.
Decreased blood pressure causes the juxtaglomeral cells (baroreceptors) of the kidneys to release renin.
Renin cleaves an inactive plasma protein called angiotensinogen to its active form angiotensin I.
Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme in the lungs.
Angiotensin II stimulates the adrenal cortex to produce aldosterone.
Aldosterone increases sodium and reabsorption of water, increasing plasma volume, increasing cardiac output, increasing blood pressure, negative feedback of the juxtoglomerular (baroreceotors).
Cortical sex hormones
Androgens and estrogens
Interesting. Male gonads secrete large quantities of androgen, so adrenal testosterone plays a relatively small role in male physiology. Females, by contrast, produce little amount of androgens from the ovaries, so females are far more sensitive to disorders of cortical sex hormone production. The same is true in the contrary for estrogen in male fetal development: males can be affected by similar disorders if they lead to excessive production of estrogens.
Functions of the corticosteroids THE THREE S’s
Salt (mineralocorticoids)
Sugar (glucocorticoids)
Sex (cortical sex hormones)
Adrenal medulla
Interior of the adrenal glands, derived from the nervous system, responsible for production of epinephrine and norepinephrine. Secrete EPINEPHRINE and NOREPINEPHRINE directly into the bloodstream. Don’t forget to associate these glands with the kidneys because they are located adjacent the kidneys.
Epinephrine and norepinephrine
Known as CATECHOLAMINES, synthesized in the adrenal medulla (adrenal medulla is derived from the nervous system, epinephrine and norepinephrine act on the nervous system). Action is centered on the fight or flight response. Epinephrine increases the breakdown of glycogen to glucose (glycogenolysis). Increases the basal metabolic rate, increase heart rate, dilate bronchi, shunt blood flow to systems that would be used in the sympathetic nervous system (increase blood flow to skeletal muscle, heart, lungs, and brain)
Pancreas
Located in upper abdomen, behind the stomach and in front of the spine. About the size of your hand.
Has both endocrine and exocrine functions.
Islets of Langerhans
Clusters of hormone producing cells. Contain alpha, beta, and delta cells.
Three types of cells in the islets of Langerhan and their products.
Alpha cell: secrete glucagon (insulin antagonist)
Beta cell: secrete insulin (promotes absorption of glucose into muscle and liver)
Delta cell: somatostatin (inhibits release of other pancreatic hormones such as insulin, glucagon, and gastrin)
Glucagon
Secreted in times of fasting. When glucose is low, glucagon increases glucose production by triggering glycogenolysis, gluconeogenesis, and degradation of protein and fat. When glucose concentrations are high, glucagon release is inhibited.
Glucagon levels are high when GLUCOSE is GONE.
Glycogenolysis
Breakdown of glycogen (a stored form of glucose)
Remember the root words of all medical terms. Glycogenolysis - lysing of glycogen.
Gluconeogenesis
Produces glucose from non carbohydrate structures such as glycerol (a 3 carbon alcohol), lactate (a metabolic bioroduct), and amino acids (building blocks of protein)
Insulin
Antagonist to glucagon. Secreted when blood glucose levels are high. Makes muscle and liver cells to take up glucose and store it as glycogen for later use. Stimulates anabolic (building) processes such as fat and protein synthesis.
Alpha cell of the islets of Langerhan
Secrete glucagon, a hormone that prevents glucose levels from getting low. Glucagon promotes glycogenolysis.
Beta cell of the islets of Langerhan
Secrete insulin, a peptide hormone that commands liver and muscle to take up glucose and store it as glycogen (a large molecule made up of many glucose molecules)
Delta cell of the islets of Langerhan
Secrete somatostatin an inhibitor of both insulin and glucagon secretion. Also decreases growth hormone (GH) secretion.
Hypoglycemia
Characterized by low blood glucose concentration. Caused by excess insulin.
Hyperglycemia
Characterized by excess glucose in the blood. Caused by underproduction of insulin, insufficient secretions of insulin, or insensitivity to insulin. Diabetes mellitus.
Polydipsia
Increased thirst. A characteristic of hyperglycemia or diabetes mellitus.
Interesting. Mellitus is Latin for “sweet” or “sweetened with honey”.
Polyurea
Increased frequency of urination. A characteristic of hyperglycemia or diabetes mellitus.
Interesting. Mellitus is Latin for “sweet” or “sweetened with honey”
Type I diabetes mellitus
Known as insulin dependent. Caused by an autoimmune destruction of beta cells of the islets of Langenhorn, resulting in low or absent insulin production. Require regular injections of insulin to prevent hyperglycemia and to permit uptake of glucose into cells.
Type II diabetes mellitus
Non insulin dependent. Result of receptor level resistance to insulin. Partially inherited, partially due to environmental factors such as high carb diet and obesity.
Gonads
Testes in males, ovaries in females.
Testes secrete testosterone in response to gonadotropins LH and FSH (stimulated by human gonadotropin release hormones hGRH).
Ovaries secret estrogen and progesterone in response to gonadotropins. Estrogen is involved in development of the female reproductive system during gestation and also promote the development and maintenance of secondary sex characteristics in females. Estrogen and progesterone also govern the menstrual cycle as well as pregnancy.
Pineal gland
Located deep within the brain. Secretes melatonin which has been demonstrated to be involved in circadian rhythms.
Pineal gland receives projections directly from the retina but is not involved with vision.
Erythropoietin
Stimulates bone marrow to increase erythrocytes (red blood cells). Produced in the kidneys.
Poietin means “substance that forms”
Atrial natriuretic peptide (ANP)
Released by heart. Helps regulate salt and water balance. Antagonistic to aldosterone because it lowers blood volume and pressure and has no effect on blood osmolarity.
Thymosin
Released by the thymus, important for proper T cell development and differentiation. The thymus is a primary lymphoid organ of the immune system.
