A&P 2 - Hormones

Posterior Pituitary Hormones

• Oxytocin

• Anti-Diuretic Hormone (ADH) / Arginine Vasopressin (AVP)

Oxytocin (Acts has positive feedback mechanism)

Type: Peptide

From: Hypothalamus

Targets: Uterus & breasts

Mechanism of action:

1. Increases contraction of uterine SMCs

2. Stimulates dilation of the cervix

3. Stimulates mammary gland => milk

Secreted: stretching of the cervix & uterus; associated w/ social bonding; estrogen has permissive effects on oxytocin receptors

Anti-Diuretic Hormone (ADH) / Arginine Vasopressin (AVP)

Type: Peptide

From: hypothalamus

Targets: Kidneys, sweat glands, & arteries

Mechanisms of action:

1. Kidneys retain water

2. Arterial vasoconstriction (helps defend blood pressure)

Secreted: osmotic pressure, dehydration, &/or decreased BV stim osmoreceptors in hypothalamus => release ADH

Anterior Pituitary Hormones

(“FLAT PEG”)

• Follicle Stimulating Hormone (FSH)

• Lutenizing Hormone (FH)

• Adrenocorticotropic Hormones (ACTH)

• Thyroid Stimulating Hormone (TSH)

• Prolactin (PRL)

• Endorphins

• Growth Hormone (GH)

Pars Intermedia:

• Melanocyte Stimulating Hormone (MSH)

Follicle Stimulating Hormone (FSH)

Type: Peptide

From: Pars Distalis – Anterior pituitary

Targets: M --> testes (Sertoli cells)   F --> ovaries (Follicular cells)

Mechanism of action:

1. M: stimulates sperm production

2. Stimulates oocyte production & follicular cells to secrete estrogen

Secreted: regulated by GNRH & GNIH

1. M: remains constant after puberty

2. F: immediately prior ovulation

Lutenizing Hormone (FH)

Type: Peptide

From: Pars Distalis – Anterior Pituitary

Targets: M--> testes       F --> overies

Mechanism of action:

M: stimulates testosterone secretion

F1: stimulates estrogen & progesterone secretion

F2: initiates (triggers) ovulation

Adrenocorticotropic Hormone (ACTH)

Type: peptide

From: Pars Distalis – Anterior Pituitary

Targets: Adrenal cortx

Mechanism of Action:

1. ACTH => adrenal cortex secretes glucocorticoids (cortisol) => stims. Catabolism of glycogen, fat, & protein (“liberate energy nutrients”) for “fight or flight” & tissue repair

Secreted: regulated by CRH & CIH; stressful stimuli such as trauma or low glucose; glucocorticoid inhibit CRH and ACTH

Thyroid Stimulating Hormone (TSH)

Type: Peptide

From: Pars Distalis – Anterior Pituitary

Targets: Thyroid gland

Mechanism:

1. stimulates the thyroid gland follicular cells to uptake iodide, synthesize T4 & T3 & increase thyroglobin synthesis

Secreted: regulated by TRH & TIH; TRH => TSH => T3 & T4; results in creased metabolism & permissive effect on catecholamine receptors

Prolactin (PRL)

Type: Peptide

From: Pars Distills - anterior pituitary (lacotropes)

Targets: mammary glands

Mechanism:

• F: initiates lactation (milk production)

Secreted: regulated by PRH & PIH; before menstruation & during pregnancy; synergistic effect with oxytocin to stimulate lactation

Endorphins

Are naturally occurring opioid peptides that bind to opioid receptors in the CNS to block pain & boost moods; they are released in response various stimuli to include: 

• Exercise --> strenuous physical activity triggers the release of endorphins, contributing to the “runner’s high”

• Laughter --> engaging in pleasurable activities can stimulate endorphins

• Pain --> endorphins alleviate pain

• Sex --> sexual activity is associated with increased endorphin levels

• Stress --> endorphins can be released in response to stress

Growth Hormone (Somatotropin)

Type: peptide

From: Pars Distalis – Anterior Pituitary

Targets: stimulates growth of all tissues & organs except the brain

Mechanism of action:

1. Stimulates mitosis & cytokinesis

2. Stimulates IGFs in liver resulting in protein synthesis in skeletal muscle, bone, & cartilage

3. Increases blood glucose & TGs

Secreted: regulated by GHRH

Triiodothyronine (T3) & Thyroxine (T4)

Type: Amine (tyrosine + iodide)

Where: thyroid gland (follicular cells)

Targets: most body tissue; CNS development!

Mechanism:

1. increase BMR (ATP formation)

2. increase lipolysis

3. stimulate protein synthesis

4. accelerates body growth

5. stimulates development of CNS

Secreted: TRH => TSH => T3 & T4

Melanocyte Stimulating Hormone (MSH)

type: peptide

from: Pars Intermedia - Anterior pituitary (melanotrophs)

Targets: melanocytes in skin & hair

Mechanism:

1. Stimulates synthesis & secretion of melanin by melanocytes => pigmentation

2. secondary effects (at hypothalamus) suppresses appetite & stem sex arousal

Secreted:

• M: remains constant

• F: constant; surges in pregnancy

Thyroid and Parathyroid Hormones

• Triiodothyronine (T3)

• Thyroxine (T4)

• Calcitonin

• Parathyroid Hormone

triiodothyronine (T3) & Thyroxine (T4)

Type: Amine (tyrosine + iodide)

From: thyroid gland (follicular cells)

targets: most body tissues; CNS development

Mechanism:

1. increase BMR (ATP formation)

2. increase lipolysis

3. stimulate protein synthesis

4. accelerates body growth

5. stimulates development of CNS

Secreted:

TRH => TSH => T3 & T4

T4 vs T3

T4 is the inactive form of T3

• T4 has longer half-life

• T4:T3 = 20:1 in blood

• T4 => T3 in target cells

• T3 is 4x more potent

Calcitonin

Type: peptide

From: thyroid gland (parafollicular / C cells)

Targets: bones, kidneys

Mechanisms:

1. stimulates osteoblasts

2. inhibits osteoclasts

3. stimulates kidneys to expel Ca2+

secreted: high blood Ca2+ levels stimulate secretion; low blood Ca2+ levels inhibit secretion

Parathyroid Hormone (PTH)

Type: peptide

From: parathyroid gland

Targets: bone, intestine, & kidney cells

Mechanisms:

1. stimulates osteoclasts

2. inhabits osteoblasts

3. stimulates kidneys & intestines to activate vitamin D & reabsorb Ca2+

Secreted:

parathyroid receptors detect Ca2+ levels

Adrenal Hormones

• Epinephrine

• Norepinephrine

• Dopamine

• Mineralocorticoids - Aldosterone

• Glucocorticoids - Cortisol

• Gonadocorticoids - Dehydroepiandosterone

Norepinephrine (NE)

Type: catecholamine & neurotransmitter (tyrosine → DOPA → NE)

From: Adrenal medulla (chromafflin cells); SNS

targets: adrenergic receptors

Mechanism:

1. binds to adrenergic receptors

2. initiate “fight or flight” responses

Secreted: CNS response to stress - physical threat, excitement, noise, bright lights, & high ambient temps

Epinephrine (EPI)

Type: catecholamine & neurotransmitter (tyrosine → DOPA → NE → EPI)

From: Adrenal medulla (chromafflin cells); SNS

targets: adrenergic receptors

Mechanism:

1. binds to adrenergic receptors

2. initiate “fight or flight” responses

Secreted: CNS response to stress - physical threat, excitement, noise, bright lights, & high ambient temps

Dopamine (DA)

Type: neurotransmitter & catecholamine

From: neurons in CNA & adrenal glands

Targets: dopamine receptors (midbrain, basal ganglia, hypothalamus, prefrontal cortex)

mechanism:

1. reward-driven learning & pleasure

2. smooth motor functioning

3. inhibits release of prolactin

Secreted: reward-seeking behavior

Mineralocorticoids - Aldosterone (ALCO)

type: steroid, mineralocorticoid

from: adrenal gland

Targets: mineralocorticoid receptors in the distal tubules & CDs of nephrons

Mechanisms:

1. unregulated renal Na-K pumps

2. reabsorption of Na ions & water

3. secretion of K ions into urine

Secreted:

low blood volume activates RAAS; helps control sodium and potassium levels

Glucocorticoids - Cortisol

type: steroid, glucocorticoid

from: adrenal cortex

targets: liver, muscle, bone, adipocytes & anti-inflammatory pathways

Mechanism:

1. stimulates protein catabolism

2. stimulates lipoylsis

3. stimulates gluconeogenesis

4. Suppresses the immune system by decreasing B-Cell antibody production & inhibit release of inflammation mediators

secreted: stress, low levels of blood glucose

Gonadocorticoids - Androgens (DHEA)

Type: steroid, gonadocorticoid

From: adrenal gland

Targets: gonads & other tissues

Mechanism:

1. Stimulates protein synthesis in muscle & bone

2. Increases spermatogenesis

secreted: masculinization of fetus; production increases at puberty

**Precursor of all estrogens

(Very small amounts of testosterone are found here)

Pancreatic Hormones

• Glucagon

• Insulin

• Somatostatin

Glucagon

type: peptide

From: pancreatic alpha cells

targets: liver hepatocytes

Mechanisms:

1. stimulates gylcogenolysis

2. stimulates gluconeogenesis

secreted: in response to low blood glucose levels (hypoglycemia)

Insulin

type: peptide

From: pancreatic beta cells

Targets: liver hepatocytes, muscle, adipose, & lots of other cell

Mechanisms:

1. stimulates glucose uptake

2. stimulates glycogenesis

3. stimulates lipogenesis

Secreted: in response to elevated blood glucose levels (hyperglycemia)

Somatostatin

Type: peptide

From: pancreatic delta cells, hypothalamus (GHIH) & GI tract

target: liver hepatocytes & GI tract (stomach)

Mechanisms:

1. inhibits / slows cell growth

2. inhibits protein synthesis

3. inhibits GI hormones

Secreted: in response to elevated levels of GH or IGF-1

5 Gonadal Hormones

• Estrogen

• Progesterone

• testosterone

• Activin

• Inhibin

Estrogen (E)

type: steroid

From: ovaries (developing follicles & corpus luteum)

Targets: everywhere

Mechanisms:

1. developed reproductive tissues

2. regulates menstrual cycle

3. maintains pregnancy

4. prepares mammaries for lactation

5. stimulates calcitonin & osteoblasts

6. inhibits PTH & osteoclasts

Secreted:

hypothalamus => GNRH & GNIH

Anterior pituitary => LH & FSH

ovaries => estrogen & progesterone

Progesterone (P)

type: steroid

From: ovaries

Targets: ovaries, uterus, breast, CNS

Mechanisms: (Maintain pregnancy)

1. develops reproductive tissues

2. regulates menstrual cycle

3. maintains pregnancy

4. prepares mammaries for lactation

Secreted: P (& E) are secreted from the corpus luteum immediately after ovulation; progesterone prepares the wall of the uterus to accept a fertilized egg for implantation & growth

Testosterone (T)

type: steroid

From: testes (Leydig)

Targets: gonads (primary sex characteristics); many tissues (2nd characteristics)

T => DHT (dihydrotestoerone)

Mechanisms:

1. before birth => maculinization

2. enlargement of male sex organs

3. expression of male 2nd sex characteristics at puberty

4. development of sexual function

5. protein synthesis

Secreted: before birth, surges during puberty, & adolescents, then decreases

Activin

IS AN ANTAGONISTS

type: Peptide

From: gonads, pituitary gland, and placenta

Targets: anterior pituitary & Sertoli cells

Mechanisms:

1. up regulates FSH synthesis

2. stimulates FSH secretions

3. stimulates spermatogenesis & oogenesis

Secreted: in response to androgens

Inhibin

type: peptide

From: gonads [corpus lute (F); sertoli & granuloa cells (M), pituitary gland & placenta

Targets: anterior pituitary (gonadotropes)

Mechanisms:

1. down regulates FSH synthesis

2. inhibits FSH secretion

3. inhibits spermatogenesis (M) & oogenesis (F)

Secreted: in response to androgens (testosterone, DHT, androstenedione)

Pineal gland hormones

Melatonin

Melatonin (MT)

type: amine

From: pineal gland

Targets: retina => pinealocytes

secrete MT => suprachiasmatic nucleus (SCN) in the hypothalamus; SCN is the body’s “biological clock”

Mechanisms:

1. promotes sleepiness

2. antioxidant

Secreted:

higher levels during childhood; hyper secretion => seasonal affective disorder (SAD);

pineal Gand = daily clock (sleep/wake)

hypothalamus = biological clock

Thymus gland hormones

• Thymopoietin

• Thymosin

Thymopoietin

HORMONE STAYS IN GLAND

type: peptide

From: thymus gland

Targets: thymus gland

Mechanisms:

1. stimulates T-lymphocytes to mature & differentiate

Thymosin

type: peptide

From: thymus gland

Targets: thymus gland

Mechanisms:

1. stimulates T lymphocytes to mature and differentiate

Unique characteristics:

imbalance is association w/ HIV/AIDS

Cardiac / Heart hormones

• Atrial Natriuretic Peptide (ANP)

• Brain (Ventricle) Natriuretic peptide (BNP)

Atrial Natriuretic Peptide (ANP)

type: peptide

From: atrial myocytes

Targets: kidneys, adrenal cortex, & vascular endothelial cells / SMCs

Mechanisms:

1. Stimulate kidneys expel Na+ (& H2O) in order to reduce BV; decreases Na+ reabsorb in DCT

2. inhabits aldosterone secretion

3. stimulates vasodilation

Secreted:

increased BV => atrial stretching => ANP release

Brain Natriuretic Peptide (BNP)

type: peptide

From: ventricle myocytes

Targets: kidneys, adrenal cortex, & vascular endothelial cells / SMCs

Mechanisms:

1. stimulate kidneys expel Na+ (& H2O) in order to reduce BV; decreases Na+ reabsorb, in DCT

2. inhabits aldosterone secretion

3. stimulates vasodilation

Secreted:

increased BV => ventricle

stretching => BNP release

Where does angiotensinogen come from?

The Liver

• It is the inactive form of angiotensin

GI Hormones

• Gastrin

• Secretin

• Cholecystokinin

• Glucose Insulinotropic Peptide (GIP)

• Glucagon-Like Peptides 1&2 (GLP)

• Ghrelin

Gastrin

type: peptide

From: G cells in stomach

Targets: parietal cells & enterochromaffin-like cells (ECL) in stomach

Mechanisms:

1. stimulates parietal cells to release H+ & Cl ions which combine with water (H2O) in the stomach to form HCL

2. HCL destroys bonds in everything

3. activates pepsinogen => proteins

Secreted:

by stomach dissension, presence of AA/proteins, & vagal stimulation

Secretin

type: peptide

From: S cells of the duodenum

Targets: parietal cells, acini cells, & hepatocytes

Mechanisms:

1. inhibits the secretion of HCL from parietal cells

2. Stimulates acini cels to secrete a bicarbonate-rich fluid into the SI to neutralize gastric acid

3. stimulates liver to produce bile

Secreted:

in response to low duodenal pH;

*antagonist to gastrin

*synergist with CCK

Cholecystokinin (CCK)

type: peptide

From: I cells in the duodenum & jejunum

Targets: pancreatic acini cells & gallbladder

Mechanisms:

1. stimulates digestive enzyme secretion

2. relaxes the sphincter of Oddi

3. initiates digestion & absorption

Secreted:

when chyme (w/ fats and proteins) are present in the duodenum; also acts as a hunger suppressant

Glucose Insulinotropic Peptide (GIP)

type: Peptide

From: K cells in the duodenum & jejunum

Targets: Pancreatic B-cells

Mechanisms:

1. stimulates insulin secretion

2. stimulates lipogenesis (occurs in adipose cells) by activating lipoprotein lipase

Secreted: glucose in chyme in duodenum

Glucagon-Like Peptide-1 (GLP-1)

type: peptide

From: L cells in the SI

Targets: alpha & beta cells in the pancreas hypothalamic GLP receptors

Mechanisms:

1. Suppresses glucagon secretion & stimulates insulin secretion

2. Promotes satiety (feeling full)

Secreted: in response to glucose in the SI

Ghrelin

type: Peptide

From: ghrelinergic cells (P/D1 cells) in the stomach & duodenum & pancreatic epsilon cells

Targets: hypothalamic ghrelin receptors

Mechanism:

1. stimulates appetite

2. stimulates GH secretion

3. stimulates reward cognition

Secreted:

increased levels prior to food intake & decreased levels after

**Antagonist to leptin

Adipose Tissue Hormones

• Leptin

• Resistan

Leptin

type: peptide

From: adipocytes (WAT)

Targets: hypothalamic leptin receptors

Mechanism:

1. suppresses hunger

2. stimulates energy expenditure

Secreted:

adipocytes synthesize & secrete leptin during lipogenesis

**Antagonist to ghrelin

Resistan

type: peptide

From: adipocytes (WAT)

Targets: liver hepatocytes & skeletal muscle

Mechanism:

1. induces insulin resistance

2. stimulates LDL-C production in liver hepatocytes

3. stimulates endothelial adhesion molecules & accelerates athrosclerosis

Secreted: adipocytes synthesize & secrete resistant during lipogenesis

Placental Hormones

• Human Chronic Gonadotropin (hCG)

• Human Placental Lactogen (hPL)

Human Chorionic Gonadotropin (hCG)

type: peptide

From: placenta = chorion

Targets: corpus lutes (ovaries)

Mechanism:

1. Placenta secretes hCG to bind w/ LHCG receptors on corpus lutes, causing secretion of Prog. & Estrog.

2. maintains pregnancy

3. inhibits uterine contraction

4. inhibits cervix dilation

Secreted:

begins 7-10 days after zygote implementation, peak level 8-10 weeks, decline 4-5 months, stable until birth

Human Placental Lactogen (hPL)

type: peptide

From: placenta

Targets: insulin receptors, livers, adipose tissue, & mammary glands

Mechanism:

1. acts as insulin antagonist & blocks maternal glucose uptake to redirect glucose to the fetus

2. inhibits gluconeogensis

3. stimulates lipolysis

4. stimulates mammary duct proliferation

Secreted:

detected by 5-6th week of pregnancy & rises steadily through 36th week

Renal / Kidney Hormones

• Erythropoietin (EPO)

• Renin => Angiotensin I & II

Erythropoietin (EPO)

type: peptide

From: renal capillary

Targets: EPO receptor on hematopoietic stem cells in bone marrow; CNS

Mechanism:

1. stimulates stem cells in red bone marrow to increase RBC production

2. involved in brain’s response to neuron injury & wound healing

Secreted:

when blood O2 is low (hypoxemia)

Renin => Angiotensin (ANG) I & II

type: peptide

From: juxtaglomerular (JG) cells in kidneys

Targets: blood vessels, renal tubules

Mechanism:

1. Renin converts angiotensinogen (a liver enzyme) to ANG I; ANG => ANG II by ACE

2. ANG II stimulates vasoconstriction (increases BP) & ALDO secretion

3. ALDO => renal tubules increase Na+ & H2O reabsorption into blood => increase BV => increase BP

Secreted: when renal BP (BV) is low