Endocrine System: Glands and Hormones

Endocrine System Overview

• The endocrine system works with the nervous system as a main control system in the body
• It is comparatively slower than the nervous system
• It formulates and releases hormones from endocrine glands.

Endocrine Glands

• Characterized as ductless glands
• Secretions (hormones) are released directly into the blood
• Hormones consequently impact distant cells
• The main endocrine glands are pituitary, thyroid, parathyroid, pancreas, suprarenal (adrenal), and gonads (testes in males and ovaries in females)
• Other organs with endocrine functions include the liver, kidneys, gastrointestinal tract, pineal gland, and placenta.
• The liver secretes erythropoietin (10%), somatomedins, and 25-hydroxycholecalciferol (vitamin D)
• The kidneys secrete erythropoietin (90%) and 1-25 dihydroxycholecalciferol (most active form of vitamin D)
• The gastrointestinal tract secretes GIT hormones such as gastrin and secretin
• The pineal gland secretes melatonin
• The placenta secretes estrogen, progesterone, relaxin, human chorionic gonadotropin (HCG) and human chorionic somatomammotropin (HCS)

Hormones

• A chemical substance secreted directly into the blood by an endocrine gland
• Hormones affect distant cells.
• Classified into three groups chemically

Hormone Classification

• Steroid group: derived from cholesterol and contains a steroid nucleus (e.g., adrenocortical hormones like cortisol, aldosterone, and sex hormones like estrogen, progesterone, and testosterone)
• Amino acid derivatives: derived from the amino acid tyrosine (e.g., thyroid hormones T3 and T4 and adrenomedullary hormones adrenaline and noradrenaline)
• Protein and peptide hormones: include hypothalamic, pituitary, parathormone (PTH), and pancreatic hormones

Mechanism of Hormone Action

• Steroid & Thyroid Hormones (T3 & T4): lipid soluble, allowing passage through the cell membrane and binding to intracellular (cytoplasmic) receptors
• The hormone-receptor complex enters the nucleus, activates gene transcription, forms mRNA, diffuses to the cytoplasm, stimulates ribosomes, and stimulates the synthesis of specific proteins
• Thyroid hormones bind directly to nuclear receptors instead of cytoplasmic receptors
• Relatively slow in action because it affects protein synthesis
• Proteins & Catecholamines Hormones: cannot pass through the cell membrane because they are not lipid soluble
• They bind to cell membrane receptors
• The binding of these hormones (first messenger) with the cell membrane receptor activates a second messenger, which mediates the hormone's activity.

Second messengers

• cAMP (Adenyl Cyclase cAMP) is a second messenger for hypothalamic releasing hormones, anterior and posterior pituitary hormones (ACTH, TSH, LH, FSH, ADH, Oxytocin), parathormone, catecholamines, and glucagon
• cGMP
• Calcium ions calmodulin
• Cell membrane Phospholipids: Hormone binding to receptors activates Phospholipase C, converting Phosphatidyl inositol biphosphate into Inositol triphosphate (IP3) or Diacylglycerol
• Prostaglandins

Hormone Transport

• Protein hormones and catecholamines circulate freely
• Non-protein hormones (steroid and thyroid hormones) circulate bound to plasma proteins, particularly globulins
• The free fraction is the physiologically active portion and is very small.

Hormone Inactivation

• Occurs in the blood, liver, or kidneys through degradation, oxidation, reduction, methylation, or conjugation to glucuronic acid
• They can then be excreted in bile (feces) or urine.

Diurnal Variation of Hormones

• Plasma levels change physiologically during the day
• Growth hormone and prolactin are low in the early morning and high in the evening
• Cortisol levels are high in the early morning and low in the evening.

Pituitary Gland (Hypophysis Cerebri)

• Located at the base of the skull in the sella turcica
• The Pituitary gland has two lobes: anterior (adenohypophysis) and posterior (neurohypophysis)
• Connected to the hypothalamussuperiorly by the pituitary stalk
• Contains two connections

Pituitary Gland Connections

• Vascular: Hypothalamo-hypophyseal portal circulation transports hypothalamic hormones to the anterior pituitary to regulate hormone secretion;
• Nervous: Hypothalamo-hypophyseal tract transports ADH and oxytocin, synthesized in the hypothalamus, for storage in the posterior pituitary.

Anterior Pituitary Gland (Adenohypophysis) Cells

• Chromatophobes (50%) contain no secretory granules
• Chromatophils (50%) contain secretory granules and splits into acidophils (40%) and basophils (10%).

Anterior Pituitary Hormones

• Trophic hormones that regulate the secretion of the thyroid, adrenal cortex, and gonads; secreted by basophils
• Includes thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), and gonadotropic hormones (GTH), like follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
• Non-trophic protein hormones that have direct metabolic effects on tissues are secreted by acidophilic cells
• Includes growth hormone (somatotrophic hormone) and prolactin (lactogenic hormone)
• There is also Melanocyte-stimulating hormone (MSH), which does not appear to have a function in humans

Regulation of Anterior Pituitary Function

• It occurs via a hypothalamic-neurosecretory mechanism
• The hypothalamus sets the level of hormones according to the body's needs.
• Neurohormones from the hypothalamus reach the anterior pituitary via the hypothalamo-hypophyseal portal circulation
• The neurohormones include growth hormone-releasing hormone (GRH), growth hormone-inhibitory hormone (GIH), prolactin-inhibitory hormone (PIH), prolactin-releasing hormone (PRH), gonadotropin-releasing hormone (GRH), TSH-releasing hormone (TSHRH) or (TRH) and corticotropin (ACTH)-releasing hormone (CRH)

More on Hormone regulation

• The levels of the hormones in the blood are maintained by the hypothalamus
• It is achieved vis a feedback control mechanism.
• High thyroid hormones (T3 & T4) levels result in decreased TSH secretion and thyroid hormone inhibition until normal levels are reached

Types of Feedback Control

• Long-loop: hormones from target endocrine glands control the hypothalamus or pituitary gland (e.g., steroid hormones and thyroid hormones).
• Short-loop: negative effects of pituitary trophic hormones on the hypothalamus.
• Ultra-short: hypothalamic releasing hormones inhibit their synthesis and release.
• Some hormones are not under the control of the hypothalamus or pituitary gland, including parathyroid hormone (PTH), calcitonin, aldosterone, insulin, and glucagon

Growth Hormone (GH), Somatotropic Hormone

• A protein similar to prolactin and human chorionic somatomammotropin (HCS)
• Metabolized partially by the liver.

Growth Hormone Effects

• Stimulates bone growth in length and thickness
• It stimulates chondrocytes in epiphyseal cartilage and osteogenic cells in bones
• It stimulates the deposition of calcium and sulfate in bones, stimulating calcification and mineralization
• The mechanism of action is mediated by somatomedin (sulfation factor), a polypeptide secreted by the liver under GH influence
• The most common type of somatomedin is somatomedin C, also called insulin-like growth factor 1 (IGF-1), which has insulin-like effects
• Regulates an increase in soft tissue mass

Impact of Growth Hormone on Metabolism

• Acts as an anabolic hormone in protein metabolism by accelerating protein synthesis and the transport of amino acids
• Induces erythropoiesis
• Has a positive nitrogen and phosphorus regulating effect
• Has a diabetogenic (hyperglycemic) effect on carbohydrates
• Affects an increase in gluconeogenesis, and the inhibition of glucose uptake by cells (anti-insulin effect)
• Stimulates alpha cells in pancreatic islets, leading to glucagon release and glycogenolysis
• Has a ketogenic (lipolytic) effect on fat
• It mobilizes fatty acids, stimulates ketone body formation in the liver, and prevents new fat synthesis

Growth Hormone Effects on Electrolytes

• Elevates GIT absorption of Ca2+
• Reduces the excretion of Na+ and K+
• Induces milk production because it has similar structural build as prolactin

Control of GH Secretion

• The hypothalamus: regulates the production of GH
• Regulates the use of GH liberating hormone (GHRH) and is also affected by: non-REM sleep, stress, exercise, hypoglycemia, pregnancy, increase in levels of sex hormones and amino acids
• Growth hormone inhibitory hormone (GHIH) restricts growth hormone discharge and is heightened in the setting of hyperglycemia, cortisone, and free fatty acids released in the blood
• Feedback Control: It is restrained in response to negative signals, and blood levels of GH and somatomedin have an influence on the discharge of the hormones

Disorders of GH Secretion

• Changes in quantity of growth hormone levels
• Causes pituitary dwarfism, an inherited condition which can be caused by surgical procedure to stop the making of GH causing an inactive GH or a lack of an organ response to endogenic GH which can cause somatomedin emission
• Causes abnormalities in bone growth at under 120cm, soft tissue which is symmetric to the symmetry of the patient along with average mental/sexual function

Pituitary infantilism

• It is dwarfism, also causes low GH and gonadotropins
• The distinction is in the organs for secondary sex function

Over Secretion of GH Causing Gigantism

• The over making of GH results in a condition of gigantism pre adolescence
• The gigantism effects all bones due to the disproportionate amount or growth effect on GH
• Muscle fatigue and over growth of soft tissue are also symptoms of gigantism

Over Secretion of GH Causing Acromegaly

• Excessive level of GH secretion after adolescence effects the hands and feet
• This includes thickening of broad hand bones

Effect on Bone Development

• The development of bone can cause protrusion or enlargement of the nose
• enlargement of the lower jaw and kyphosis

Prolactin (Mammatropin)

• Identical in construction to GH
• Key for stimulation, to make milk happen and is an increase of the amount of body fat

Key Aspects of Prolactin

• The encouragement for a parents conduct
• Reproduction by a decrease of amounts of GRH and reduction of hormone secretions
• This process causes reduction of sex hormones also with reduction to libido

Regulation of Prolactin Emission

• The control of PRH and Hypothalmus
• Hyporthalamus inhibits Prolactin secretions
• Prolactin has a negative feedback in quantities and increases in response to sleep, stress, or as a result of less blood sugar issues
• Elevated production of estrogen will also heightened how much prolactin is made, however, reduction hormone creation may increase with a sucking baby from lack of the hormone

Ailments with Release of Prolactin

• This usually effects woman and often causes reduced making of milk
• Over hormone production is as result of adenomacells within other sections of the body

Hyperprolactinemia

• Usually effects women and causes formation of milk outside a normal pregnancy or breast feedings which causes non-fertility of woman
• Effects males with abnormal function

Treatments for Hyperprolactinemia Hormones

• Medication for hormone and tumor removal

Stimulating Hormones (MSH)

• A poly structurally related to to adrenocorticotropic hormone
• Its primary working is by managing skin tone and endocrinal problems from the result of secreting MSH and ACTH
• Its lack causes pale skin or hormone production can effect skin pigment issues

Panhypopituitarism (Simmonds Disease)

• This disease can also be called pituitary Cachexia to a removal of function
• It is caused by tumor functions reducing hormone function as well

Symptoms Panhypo Pitutiarism

• Low blood cell numbers
• Loss of hair and bad skin ailments
• Infertility concerns and bone concerns leading to other health risks

posterior pituitary gland

• Posterior of pituitary gland can make 2 secretions of oxytocin and vasopressin
• These hormones are formed in the hypothalamus with key relation to function of the adrenal gland

Vasopressin

• The hormones are kept due to the function of hypo adrenal gland
• Made by sending hormones from the adrenal glad to the kidney for fixed tissue

Anti-Diuretic Hormone(ADH)

• Functions by regulating quantities and absorbing water
• Vessels are limited due to Myocardial Issues

Control of ADH hormone secretion

• Blood level varies by secretion and can determine the amount of reobsorption
• Influences on blood by reducing fluids that can trigger a release to hormones

ADH secretion

• Heat causing high function of hormone and can also influence stress by raising the functions

Ailments to Hormone Discharge

• A disease with symptoms
• Pituitary, neurogenic due to nuclei and nerve issues reducing AD hormone discharge
• Other effect can influence the renal function
• High Urination

Oxytocin Hormone

• Stimulates labor hormone with breast and uterine implications

Functions of Glands w/ Oxytocin

• Milk production with labor from the nerve function influencing the adrenal function for contraction

Thyroid Gland

• Located within gland tissue and built with key functioning with secreting follicle cells
• Involves formation with thyroglobulin with hormone production

Cell Interaction & The Adrenal Function

• Thyroid function created as secretions

Production of Hormones

• Hormone creation from the gland causes TSH to stimulate inorganic tissues and is influenced from thryocinate

Production of the Thyroid

• Oxidation forming a key function
• Union to form key function with enzyme action

Preservation Of Hormones

• In the gland unless destruction happen from hormone conditions

Hormone Actions

• Is an interworking function of components to cells

Hormones in Blood Function

• Hormones in blood operate in multiple stages

Functioning

• Functioning from multiple formations from the hormones
• This is prevented while having high level in urine

Thyroid Secretions

• High in function by producing thyroid function with functions throughout the day

iodine actions

• Iodide aids formation of the thyroid with a lack of the hormones can effect the body

Hormone Actions

• High consumption by thyroid hormones which increases consumption by tissues
• Affecting and increasing glucose and can effect protein and the lipids in the system

Actions in the Blood Cell system

• The hormone can result in anemia and a deficiency of tissue of pigment in the face

Hormone Functions

• A catalyst for the nervous and skeletal actions

Functioning Of Growth

• Functioning by T3 with lack of it, causes severe abnormalities

Hormone Ailments

• Hypothyroidism result in lower functions, or an issue that can be related to early pregnancy

Cause

• Issues resulting in lower gland operation results in an secondary issue of TSH secretions

Bone System

• Reduction of bodily function
• Muscle issues

Cretinism

• Disease of Hypothyroidism causing hormone problems
• Early births may have complications causing hormone level issues

Key Actions For Pregnancy

• Body function
• Abnormal function
• Mental issues
• Sex Organ functions

Distinctions Of Functions On dwarfism

• Is linked with thyroid and dwarfism
• It is related to hormone imbalance

Action functions of The Bone systems

• Bone system damage due from under production creating mental problems and sex organ functions

Goiler

• Relates to Thyroid Enlargement
• It is associated to bodily impact creating hormone secretion

Formation Functions

• Hormone concentration through functions and components

Non functions in thyroid creation

• It is bonded with blood to create thyroid effects with high pH

Calcium

• Effects muscle tissues and the intestines directly by glands by bones creating it

Creation OF Functions

• Stimulation from osteoclast hormone interaction

Ingestion

• Aid by absorption and hormone function for tissues

Formation

• It influences bone function and hormone functions
• This process can influence other gland as 1.25 vitamin issues
• It makes components and key functionality with tissue function
• The functions of these functions cause a product with tissue function

Control

• Hormone performance of cell tissue and pH factors that may cause other functions with bodily interactions

Muscle Interaction

• Hormone operations for phosphate hormone function
• The performance and release of calcium causing many functions
• This formation interacts key component

Hormones

• Bone function
• Lowered intestine functions
• This gland interacts key components of thyroids

Tissue Functions

• Regulation functions for cells
• Regulates cells with phosphate and can cause a function when they are elevated

Glandular Function

• High function may cause high secretion

Vitamin Function

• Functions by producing a fat soluble tissue with multiple areas for operation

Ailment of Vitamin D

• Functions in multiple body area at bone creating its function with hormonal action

Disturbance with functions

• A disease cause by muscle function causing tension and functions to effect muscle use
• Is a state created by low level intakes
• It influences functions in organs as issues to autoimmune conditions

Actions due to muscle deficiency or autoimmune of the body the actions with ailments for bone system

• Bone contractions from cramping that effect function for hands with function loss and wrist functions that effect finger motions
• Breathing from muscular motions
• All general functions effected
• Attacks

latently

• Muscle tension
• The titanic functions and can effect physical functions to cause stress to physical motion

Diagnostics

• This function cause body tests to serum and calcium to have a test given by the bodily movements

Treatments

• By addressing calcium level directly
• Treatments include multiple products and treatments that aid multiple bodily functions
• Other conditions can be aided with this action

Hypoparathyroidism

Calcium Ailment issues

• These effects can cause other diseases
• Problems with function from adrenal and tumor growth

Addison's Disease Function

Adrenal gland

• Effects cortex for normal functions
• Glands cause abnormalities to cortisol section to the core body
• The location influences key actions

The Main Gland

• Consist bodily sections with core operations
• Operations from metabolic functions such as influence function in fat. Carbohydrates and proteins to help cell creation by hormone and function regulation

Glandular Effects

• Help increase water levels that help support the body better

Corticosteroid Actions

• Influence the amount for cortisone

Action for the Gland

• Ailments with a function

Effects For The Organs

• Can influence vessels in the body to create issues with cholesterol

Gland

• Hormone production in areas that can cause a function
• It is essential that those hormones exist for body and cortisol function through sex characteristics through abnormalities

Ailments for Hormone production

• Abnormal function and growth from issues forming bodily dysfunction and functions

Ailments

• Increase the body in size
• It causes key functions that occur from growth of tissue

Overproduction of growth

• A side effects form overproduction
• Bone mass is increased by abnormalities
• Those with sex abnormalities

Sex characteristics production

• Production by hair and bodily actions

Production of The Body

• Functions to sex organs
• High amounts of secretion
• Dysfunction
• Abnormal growth

Adrenal Madulla

• Aid operation by mass discharge

Hormone secretion

• Aid operation from the sympathetic system

Metabolic Actions

• Transporters aid in the distribution for cell function

Hormones

• Has a relationship to adrenaline that is a core element of bodily functions

Hormones & Adrenalin

• This process promotes a high function to BMR and causes a tumor to form

Functions of Cell Production

• Creating cells in other places that have core effects
• This process influences sugar levels in the blood
• Hormone secretion influence GH cell
• Production of cell secretion

Gland Operations

Fat Tissue

• Increasing amino acid
• Stimulating and promoting insulin

Blood operations

• Influence high secretions and performance

Creation Operation

• Creating action for hormone to effect function tissue

Action creation

• Aid action to muscle for cell walls that effects high range of hormones
• Causing tension to bodily activity

Creation effect

• Creation and aiding effect due action of core components
• Body actions to insulin

Formation action

• Increasing creation function that supports performance

Insulin

• Reduced production

Aid secretion

• Reducing cell function of bodily operation

Actions

• Creating and operating function for core performance
• Reduce blood flow

Production of Hormone

• Reducing operation performance 5