EndoPituitary

Question 1

POSTERIOR PITUITARY HORMONES

Answer 1

Vasopressin

Oxytocin

Question 2

Vasopressin

Answer 2

antidiuretic hormone, ADH

Question 3

Vasopressin (3 things)

Answer 3

To conserve body water and regulate osmotic pressure of body fluids
Dehydration leads to increase in osmolarity, activates osmoreceptor in brain & ADH secretion
ADH acts on kidney cells (distal convoluted tubule and medullary collecting ducts) via cell surface receptors and cAMP formation; enhances water permeability and reabsorption

Question 4

DeficiencyofADH

Answer 4

CentralDiabetesinsipidus(vsnephrogenic)– inability to retain water, excess thirst, frequent urination.
Treatments: drugs (clofibrate) to increase ADH secretion and (chlorpropamide) to increase kidney response to ADH

Question 5

Excess ADH

Answer 5

Excesswaterretention,headache,drowsiness,nausea.

Treatments: drugs (butorphanol) to decrease ADH secretion and (demechlocycline) to reduce kidney response to ADH.

Question 6

Oxytocin (3 things)

Answer 6

• stimulates the contraction of smooth muscle cells, particularly that of the mammary gland and uterus (important for female reproduction)
• upon nursing, suckling reflex stimulates oxytocin release, which causes contraction of myoepithelial cells in breast to expel milk
• during child birth, oxytocin release during labour to stimulate rhythymic uterine contractions; clinically used to induce labour and therapeutically postpartum to decrease bleeding

Question 7

Hypothalamic factors control

Answer 7

anterior pituitary hormone secretion via hypophyseal portal vessels

Question 8

Major hypothalamic (hypophysiotropic) hormones (6)

Answer 8

Corticotropin-releasing hormone (CRH)
Thyrotropin-releasing hormone (TRH)
Gonadotropin-releasing hormone (GnRH) Growth hormone-releasing hormone (GHRH)
Somatostatin Dopamine

Question 9

Pulsatile/rhythmic secretion of hypothalamic and pituitary hormones

Answer 9

due to fluctuation of neuronal activity

Diurnal (24-hour) pattern of hypothalamic and pituitary hormone secretion

Question 10

Physiological and clinical significance of Pulsatile hormone secretion

Answer 10

Maintain target organ sensitivity, e.g., prevents down-regulation of receptors.
Abolish pulsatile secretion results in diminished hormone secretion, e.g., GnRH agonist leads to clinical castration (see later for details)

Question 11

Anterior pituitary hormones

Answer 11

prolactin, growth hormone, thyroid stimulating hormone, acth, gonadotropins (LH, FSH)

Question 12

Growth Hormone (Normal) GH-N

Answer 12

Somatotropes & somatomammotropes of anterior pituitary

look at actions of GH slide

Question 13

gigantism

Answer 13

if GH excess occurs early in life

Question 14

acromegaly

Answer 14

(excess soft tissue hyperplasia) if GH excess

occurs after body growth stopped

Question 15

somatotrope tumor (on acromegaly and gigantism too) metabolic syndrome

Answer 15

insulin resistance type 2 diabetes

Question 16

primary GH deficiency

Answer 16

Hypothalamic (GHRH deficiency) & pituitary lesions (tumor, injury, infection, congenital & genetic defects)
proportional short-stature if occurs early in life;
adult hypopituitarism: weakness, fine wrinkling & pale skin; loss of sex drive, genital atrophy, menstrual cycle cessation.
Other causes of retarded growth (i.e., GH is good):
GH receptor defect in target tissues (Laron Dwarfs); IGF-1 deficiency (African pygmies)
Treatment: GH and IGF-1 replacement
Hypochondroplasia

Question 17

hypochondroplasia

Answer 17

(achondroplasia), non-proportional short stature

Question 18

prolactin source

Answer 18

lactotropes, and somatomammotropes of anterior pit

Question 19

prolactin action (4)

Answer 19

• Promotes growth & function of mammary gland–milk production (also participates in suckling reflex);
• Increased maternal behaviour;
• Inhibits gonadotropin secretion/action in gonads– steroidogenesis.
• Numerous effects in lower species but not well studied in humans.

Question 20

prolactin control

Answer 20

Predominantly inhibited by hypothalamic Dopamine; Also stimulated by oxytocin, TRH, VIP & estrogen.

Question 21

hormone changes in suckling reflex

Answer 21

less dopamine acts on the anterior pituitary to produce more prolactin and then milk is produced.
more oxytocin in the post pit which cause contraction of myoepithelial cells for milk ejection

Question 22

excess prolactin

Answer 22

Hyperprolactinemia : most common form of pituitary hyperfunction caused by adenomas of lactotropes (most common form of pituitary tumor);
Dopamine receptor blockers (some psychiatric medications); Stress; high physical activities; under weight

Question 23

too much prolactin on females

Answer 23

anti-gonadal action causes secondary amenorrhea (cessation of menstrual cycle), hence infertility.
galactorrhea (inappropriate milk production);

Question 24

too much prolactin on males

Answer 24

impotence, decrease sperm count; infertility

Question 25

pituitary tumor

Answer 25

Note: all pituitary tumors can cause neurological symptoms such as vision impairment, headache, etc
Treatment: dopamine agonists (Cabergoline and Bromocryptine/Parlodel) suppress prolactin secretion & shrink prolactinomas!
Deficiency of prolactin is rare.