Endocrinology - Exam 1 (Growth Hormone & Prolactin)

The anterior pituitary is mostly composed of what kind of cells? What is the name of the hormones they sescrete?

Endocrine cells (trophic cells)

-- Trophic hormones (because they turn on or off the funciton of other endocrine glads)

NOTE: If you see "trophic"; ALWAYS think Ant. Pituitary

What two types of stimulation to the anterior pituitary is used between the hypothalamus and anterior pituitary?

Neural
Endocrine/Hormonal

What is the special system of blood vessels that ONLY exists between the hypothalamus and the anterior pituitary? Why?

Hypothalamic-Hypophysial portal system
-- so the hormones stay concentrated and only interact with the anterior pituitary not travel/interact with rest of body

What two hormones does the hypothalamus produce and release? What is their response?

Hypothalamus releasing hormone - (stimulating)
Hypothalamus inhibiting hormone - (inhibiting)

What are the 5 Releasing hormones of the Hypothalamus?

1) Growth hormone releasing hormone (GHRH)
2) Prolactin Releasing Hormone (PRH) / Prolactin Releasing Factor (PRF)
3) Thyrotrophin Releasing Hormone (TRH)
4) Corticotrophin Releasing hormone (CRH)
5) Gonadotrophin Releasing Hormone (GnRH)

What are the 2 Inhibiting hormones of the Hypothalamus?

1) Somatostatin (Growth Hormone inhibiting Hormone (GHIH))
2) Dopamine (Prolactin Inhibiting Hormone (PIH))

What is the target cell that the hypothalamus hormones target in the anterior pituitary? What do they cause?

Thyrotropes
-- stimulate/inhibit synthesis & secretion

What are the 5 trophic cell types that exist in the anterior pituitary?

1) Somatotrophs
2) Lactotrophs (mammotrophs)
3) Thyrotropes
4) Corticotropes
5) Gonadotrophs

Which hormones of the anterior pituitary are Acidophils? Which are Basophils? (based off of staining)

Acidophils = Somatotrophs & Lactotrophs

Basophils = Corticotropes, Thyrotropes, Gonadotrophs

What hormone from the Hypothalamus stimulates Somatotrophs in the Ant. Pituitary?

Growth Hormone Releasing Hormone (GHRH)

What hormone form the Hypothalamus inhibits Somatotrophs in the Ant. Pituitary?

Growth Hormone Inhibiting Hormone (GHIH / GIH) / Somatostatin (SRIH)

What hormone does Somatotrophs release from the Ant. Pitutary?

human growth hormone (hGH)

What is the function of Human Growth Hormone (hGH), which is released from Somatotrophs? (2)

• Provide adequate nutrients for ATP synthesis and protein synthesis
• Cell proliferation & differentiation

What hormone from the Hypothalamus stimulates Corticotrophs in the Ant. Pituitary?

Corticotrophin Releasing Hormone (CRH)

What does Corticotrophs in the anterior pituitary secretes?

Adrenocorticotrophic hormone (ACTH)

What is the target of the Adrenocorticotrophic hormone (ACTH) once released from Corticotrophs?

3 layers of adrenal cortex

What hormone does each of the three layers of the adrenal cortex release?

Layer 1 = Aldosterone
Layer 2 = Cortisol
Layer 3 = Androgens

What is the function of ACTH (Adrenocorticotrophic hormone)?

• Metabolism of glucose, proteins & fat

• Regulating salt & water (BP)

What hormone from the Hypothalamus stimulates Thyrotrophs in the Ant. Pituitary?

Thyrotrophin Releasing Hormone (TRH)

Thyrotrophs in the anterior pituitary secrete what hormone?

Thyroid Stimulating Hormone (TSH)

What is the target of the TSH (thyroid stimulating hormone)? What does this cause to be released and what do these hormones do?

Thyroid Gland
-- release of T4 & T3 (Thyroxine & Triiodothyronine)

--> controls most intracellular chemical rxns in body

What hormone from the Hypothalamus stimulates Lactotrophs/Mammotrophs in the Ant. Pituitary?

Prolactin Releasing Hormone (PRH/PRF)

& little affect from Thyroid Releasing Hormone (TRH)

What hormone from the Hypothalamus inhibits Lactotrophs/mammotrophs in the Ant. Pituitary?

Dopamine/PIH

Lactotrophs/Mammotrophs in the anterior pituitary secretes what hormone?

Prolactin (PRL)

What is the target of the Prolactin (PRL) once released form Lactotrophs/Mammotrophs? What does it cause/function to do?

Mammary glands

• Development & milk production

What hormone from the Hypothalamus stimulates Gonadotrophs in the Ant. Pituitary?

Gonadotrophin Releasing Hormone (GnRH)

Gonadotrophs in the anterior pituitary secretes what TWO hormones?

Follicle stimulating hormone (FSH) & Luteinizing Hormone (LH)

What effect do the Follicle stimulating hormone (FSH) & Luteinizing Hormone (LH) secreted by the Gonadotrophs have on the Ovaries? Testes?

Ovaries --> estrogen & progesterone (oogenesis)
Testes --> Testosterone (spermatogenesis)

The cell bodies of GHRH (Growth Hormone Releasing Hormone) and GHIH (Growth Homrone Inhibiting Hormone/Somatostatin) are located in what nucleus of the hypothalamus?

Arcuate nuclei

What is the process by which the hypothalamus affects the Somatotrophs?

1) GHRH released form arcuate nucleus of hypothalamus
2) Circulates via hypothalamic-hypophyseal portal system to anterior pituitary
3) Acts on Somatotrophs
4) Synthesize/secrete Growth hormone

What kind of hormone is GHRH (Growth hormone releasing hormone)? What mechanism does it use? (2)

Protein hormone
-- Phospholipase C & Adenylyl cyclase mechanism

What kind of hormone is GHIH (Growth hormone inhibiting hormone/Somatostatin)?

Peptide hormone

What kind of hormone is hGH (human growth hormone)? What mechanism does it use?

Protein hormone

• tyrosine kinase mechanism

What 5 factors stimulate GHRH (Growth hormone releasing hormone) to be released?

1) Increased amino acids i blood
2) Decrease glucose in blood (hypoglycemia)
3) Decrease fatty acid levels in blood
4) Exercise
5) Healthy stress

What 2 factors stimulate Growth Hormone Inhibiting Hormone (GHIH/Somatostatin) to be released from hypothalamus? What two molecules can also stimulate GHIH?

1) Hyperglycemia
2) High fatty acid levels

Growth hormone & somatomedin (negative feedback loop)

In addition to somatostatin inhibiting growth hormone secretion by anterior pituitary, it can have an inhibitory effect on what?

inhibits variety of physiological functions in GI tract

What hormone is secreted throughout our life span, is most imporant hormone for normal growth up to adulthood, provides adequate nutrients for ATP synthesis and protein synthesis, and has major effects on cellular proliferation and differentiation?

human Growth Hormone

T/F: hGH is secreted at a constant rate all day.

FALSE
-- pulsatile pattern (bursts every 2 hours; with largest birst about 1 hour before sleep)
-- changes over lifetime (ex: increase during birth/early childhood and large burst at puberty; stable throughout; declines as elderly)

When hGH is released by the anterior pituitary and will circulate in the blood stream, some moves on to be converted into IGF-1. The rest will affect what 4 areas of the body?

1) Adipose
2) Liver
3) Skeletal Muscles
4) Bone

What is the major effect of hGH in Adipose?

Trigger hormone sensitive lipase (HSL) to cut triglyceride into glycerol & fatty acids (can be used to make ATP)

NOTE: the glycerol goes to the LIVER

What are the 2 effects of hGH in the Liver?

1) Increased Gluconeogenesis, Glycogenolysis, and IGF-1 Production
2) Increase blood glucose levels

What are the 2 effects of hGH in the Muscle?

1) Increase AA and glucose uptake
2) Increased muscle size due to increased protein synthesis

What are the 3 effects of hGH in Bone?

1) Increase glucose uptake & AA uptake (Increase protein synthesis)
2) Increase bone mineral density
3) Chondrogenesis (puberty) --> Bone grow in LENGTH

What affect does aging have on the level of growth hormone? What pathology can this result in?

Decreases GH
-- can result in osteoporosis

What is IGF-1? what is another name for it and how is it produced?

Insulin-like growth factor 1
(Somatomedin 1)

Made in liver since some GH will go to liver to be converted

What is the function of IGF-1? What 3 areas of the body does IGF-1 have an effect on?

Bind to insulin receptors (tyrosine kinase receptor) to increase glucose uptake

Effects:
1) Muscle
2) Bone
3) Cartilage

What effect does IGF-1 have on the muscles?

Open channels for AA to be taken into the muscle for protein synthesis

What 3 effects does IGF-1 have on the bones?

1) Increases osteoblast & osteoclasts
2) Increase endochondral ossification (bigger/thicker bone)
3) Increase protein synthesis of collagen type 1

What 2 effects does IGF-1 have on cartilage?

1) Increase size, differentiation, proliferation of chondroblasts
2) increase linear growth

IGF-1 can exert what type of feedback on the release of GHRH?

Negative feedback

How does Growth Hormone INCREASE blood calcium? INCREASE immune response? INCREASE oxygen transport?

Ca -- Increase intestinal absorption of calcium
Immune -- increase number of structures producing antibodies
O2 -- increase synthesis of Erythropoietin

What is growth hormone deficiency in children called?

Dwarfism or Pituitary Dwarfism

What are 5 causes of GH deficiencies in children (dwarfism)?

1) Damage to pituitary
2) Damage to hypothalamus
3) Gene mutation
4) Head trauma
5) Brain tumor

What are 6 symptoms of GH deficiencies in children (dwarfism)?

1) Immature appearance compared to peers
2) Chubby body build
3) Prominent forehead
4) Plotting height & weight on chart, height falls behind
5) Less than 2 inches a year
6) Puberty maybe late or not at all

What are 3 complications of GH deficiencies in children (dwarfism)?

1) Decrease energy level
2) Cardiovascular risk function
3) Decreased bone density

What is a treatment of GH deficiencies in children (dwarfism)?

Injections of synthetic human growth hormone
-- can involve many years of synthetic growth hormone

What is a GH deficiency in adults called?

Adult Growth Hormone Deficiency (AGHD)

What are 4 causes of GH deficiencies in adults (AGHD)?

1) Damage to pituitary gland or hypthalamus
2) Surgery
3) Radiation
4) Blood supply to the pituitary

What are 5 complications/symptoms of GH deficiencies in adults (AGHD)?

1) Reduced bone density
2) Decreased muscle mass
3) Decreased sexual function
4) Higher level of body fat -- around waist
5) Higher level of LDL's

What is the treatment of GH deficiencies in adults (AGHD)?

hGH injections

What is a growth hormone over production (excess) in children called?

Gigantism (Giantism)

What is the cause of Gigantism in children?

Too much growth hormone released due to non-malignant tumor

What are the complications of Gigantism in children?

Usually large growth during childhood before growth plates close

What are 8 symptoms of GH excess in children (Gigantism)?

1) Delayed puberty
2) Vision difficulties
3) Frontal bossing
4) Headaches
5) Increased sweating
6) Large hands & feet
7) Galactorrhea-flow of milk from breast unrelated to childbirth or nursing
8) Weakness

What are 2 treatments of GH excess in children (Gigantism)?

1) Removal of tumor
2) Medications such as somatostatin (inhibits GH)

What is overproduction of GH in adults called?

Acromegaly (adult onset)

What is the cause of excess GH in adults (acromegaly)?

Noncancerous tumor in pituitary gland
(Adenoma)

What are 4 complications/symptoms of excess GH in adults (acromegaly)?

1) Swelling/enargement of extremities, jaw, nose, suipra orbital bulging, tongue, lips, or other soft tissues
2) Headaches, vision defects (blurring), voice deepens
3) Skin tags, profuse sweating, diabetes
4) Dental problems

What are the 3 treatments of excess GH in adults (acromegaly)?

1) Radiation
2) Medication to reduce GH
3) Surgery (hypophysectomy: remove pituitary gland)

What nucleus in the hypothalamus is Prolactin Releasing Hormone (PRH/PRF) released from? What nucleus is Dopamine/PIH released from?

PRH/PRF: Paraventricular nucleus

DA/PIH: Arcuate nucleus

What is the 4 step process by which PRH is released from the hypothalamus?

1) Released from Paraventricular nucleus
2) travels in hypothalamic-hypophyseal portal system
3) Acts on lactotrophs of Ant. pituitary
4) Synthesize & release Prolactin (PRL)

NOTE: Dopamine/PIH same pathway except released from ARCUATE nuc and inhibits PRL

Males and non-lactating females have _ levels of circulating Prolactin?

Low levels

What type of hormone is PRH (Prolactin Releasing Hormone)? What mechanism does it use?

Peptide hormone
-- Phospholipase C

What type of hormone is Dopamine/PIH? What mechanism does it inhibit?

Amine hormone
-- inhibition of adenylyl cyclase mechanism

What type of hormone is Prolactin (PRL) which is secreted by the lactotrophs? What mechanism does it use?

Peptide hormone
-- Tyrosine kinase mechanism

What are the 3 primary functions of Prolactin?

1) breast DEVELOPMENT
2) Lactogenesis
3) Inhibition of OVULATION

What is the major hormone responsible for milk production? Milk letdown?

Milk PRODUCTION = Prolactin
Milk LETDOWN = Oxytocin

At puberty, what three hormones stimulate proliferation and branching of the mammary ducts?

Prolactin, Estrogen, & Progesterone

During pregnancy, Prolactin, Estrogen, and Progesterone stimulates the growth and development of what structure, which produces milk once parturition occurs?

Mammary alveoli

Why doesn't lactation occur during pregnancy if Prolactin levels are high during this time? How does this change at birth?

High levels of estrogen & progesterone down-regulate prolactin receptors in breast and block prolactin action

-- Estrogen & Progesterone levels drop and their inhibition ceases, allowing stimulation go lactogenesis by prolactin

What type of feedback loop is breastfeeding in relation to prolactin?

Positive feedback loop

Baby suckles --> nerve sent to mothers brain --> pituitary secretes PRL --> ammary glands stimulated --> produce milk --> encourages child to suckle more

How does Prolactin (PRL) inhibit ovulation?

Inhibits synthesis & release of GnRH (Gonadotropin-releasing hormone)
--> INHIBITS gonadotrophs to secrete FSH and LH

What does too high of prolactin levels in males cause?

Parallel inhibitory effect on GnRH secretion and spermatogenesis, resulting in infertility

What causes a deficiency of Prolactin (2)? What does a deficiency cause?

Destruction of entire anterior lobe of pituitary or selective destruction of lactotrophs
-- Cause failure to lactate

What 3 things can causes an excess of Prolactin to be released?

1) Destruction of hypothalamus
2) interruption of the hypothalamic-hypophyseal tract
3) Prolactinomas (Prolactin-secreting tumors)

Why does increased prolactin secretion occur when the hypothalamus is destroyed or the hypothalamic-hypophyseal track is disrupted?

Loss of tonic inhibition by dopamine

What is the 2 major symptoms of excess prolactin secretion?

Galactorrhea
Infertility

How can excess prolactin secretion be treated?

Bromocriptine
(DA agonist that inhibits prolactin secretion by Ant. Pituitary)