Lecture 15: Pituitary, Hypothalamus, Growth

Question 1

Tropic hormone

Answer 1

Stimulates secretion of another hormone

Question 2

Trophic hormone

Answer 2

Stimulates/maintains growth of a target gland/organ

Question 3

Hypothalamus/pituitary arrangement

Answer 3

Hypothalamus under brain
Pituitary in sella turcica
Ant. pit. = adenohypophysis; oral mucosa
Post. pit. = neurohypophysis; neural tissue

Question 4

Posterior pituitary hormones

Answer 4

Oxytocin (OCT), ADH

Question 5

Anterior pituitary hormones

Answer 5

ACTH, PRL, TSH, FSH/LH, GH

Question 6

Anterior pituitary structure

Answer 6

• Releasing/inhib. factors secreted to portal system
  Pros:
  1. Direct hypothal.-pituit. comms
  2. Less secreted material needed to reach high concen.
  3. Specificity

Question 7

Neuronal inputs to pituitary

Answer 7

• Temperature
• Glucose levels
• Osm
• Pain from thalamus
• Visual cues (optic system)
• Emotions (limbic system)

Question 8

ADH (vasopressin, AVH)

Answer 8

• From post. pit.
• Stim. by increased Osm or decreased H2O (Osm/baroreceptors)
• Upreg. renal H2O reabsorption
• Disorder: diabetes insipidus

Question 9

Oxytocin

Answer 9

• From post. pit.
• Stim. by infant suckling -> milk ejection from mammary lgand
• Stim. by cervical dilation in labor -> uterine contractions

Question 10

FSH, LH

Answer 10

• From ant. pit. gonadotropes
• Germ cell development, sex hormone secretion

Question 11

GH

Answer 11

• From ant. pit. somatotropes
• Stim. IGF-1 secretion from liver/others
• Stim. metabolism for growth; protein synth., skeletal growth

Question 12

TSH

Answer 12

• From ant. pit. thyrotropes
• Stim. synth. + release of T3, T4 -> increase BMR

Question 13

PRL

Answer 13

• From ant. pit. lactotropes
• Stim. breast development, milk production in women
• Feedback inhib. for GnRH in men + women

Question 14

ACTH

Answer 14

• From ant. pit. corticotropes
• Stim. cortisol secretion from adrenal cortex (stress hormone)

Question 15

Hypothalamus releasing factors (stim. by neuronal input)

Answer 15

• GnRH -> gonadotrophs
• GHRH -> GHs from somatotrophs
• SST –| somatotrophs
• TRH -> TSH, PRL
• Dopamine –| PRL –| GnRH
• CRH -> ACTH

Question 16

3 major causes of hyporesponsiveness

Answer 16

1. Receptor deficiency
2. Post-receptor defect
3. Lack of metabolic activation of hormone

Question 17

5α-reductase deficiency

Answer 17

Responsible for activation of T to DHT

Question 18

Hypersecretion

Answer 18

Caused by pituitary tumors. Functional adenoma -> hypersecretion of ant. pit. hormones
Non-functional tumor -> tissue compression, vision impair., neuro complications

Question 19

GH secretion pattern

Answer 19

Pulsatile secretion; must measure over time
- Triggered by sleep, stress, exercise, fasting, Arg, low gluc.
- Male GH more pronounced in early sleep hours vs females

Question 20

GH actions

Answer 20

• Bone lengthening (epiphyseal plate)
• Protein synth. (AA uptake)
• Anti-insulin effects:
  1. Inhib. muscle gluc. uptake
  2. Stim. liver gluconeogen.
  3. Stim. adipose lipolysis
  Hypoglycemia -> GH rise; acromegaly gluc. tolerance test

Question 21

IGF-1

Answer 21

• Production stim. by GH
• Stim. cell division, bone growth
• Neg. fb on pituitary; IGF-1 levels correlate w/ GH

Question 22

Leron’s dwarfism

Answer 22

GH-R defect leading to low IGF-1 with normal GH levels

Question 23

Permissive hormones for GH

Answer 23

• Thyroid hormone
• Insulin
• Glucocorticoids
• Sex steroids

Question 24

Thyroid hormone and GH

Answer 24

TH req. for sk. maturation/growth
- No growth promotion w/o GH
- Stunted growth w/o TH
Thyroid hormone increases GH synth., GHRH-R on somatotropes
- GH –| TH

Question 25

Insulin and GH

Answer 25

- In utero: insulin req. for fetal growth to activate IGF-1 receptors - Post-partum: req. for normal growth only w/ GH

Question 26

Glucocorticoids and GH

Answer 26

- Req. for GH synth., normal growth - Excess stress --| GH secretion; stress can be detrimental to growth; psychosocial dwarfism

Question 27

Sex steroids and GH

Answer 27

Androgens -> estrogen via aromatase req. for: - Puberty growth spurt (increased GH, IGF-1) - Accelerate growth at puberty start, close epiphysis @ end

Question 28

Gigantism vs acromegaly

Answer 28

Gigantism = before puberty Acromegaly = after puberty (after epiphyseal plates close)

Question 29

Non-endocrine factors on growth

Answer 29

- Genes, nutrition, disease, stress - Avg parental height

Question 30

Mid Parental Height

Answer 30

Parent avg +/- 2.5 inches (dpdt on male/female) Also 2 SD range (+/- 4 inches) = MPH; 50th percentile for family