Week 3: Anterior pituitary hormones, growth hormone

Question 1

Actions of prolactin and regulation of release

Answer 1

• promotes milk secretion and maternal behavior, released by lactotrope cells
• stimulated by: suckling, TRH, moderate levels of estrogen
• inhibited by: dopamine (tonically inhibited by dopamine)

Question 2

regulation of LH and FSH release

Answer 2

• stimulatory: GnRH-gonadotropin releasing hormone

- inhibitory: negative feed back from estrogen and testosterone, prolactin

Question 3

Hyper and hypoprolactinemia

Answer 3

• hypoprolactinemia: from pituitary damage
• hyperprolactenemia: often from prolactinoma, most common pituitary tumor. Can lead to infertility, amenorrhea, galatorrhea, and hypogonadism in women. In men, can lead to impotence, infertility, increase in breast size.
• can treat prolactinoma with dopamine against such as bromocriptine to inhibit secretion.

Question 4

Effects of growth hormone

Answer 4

• GH is pulsatile. Can work directly or indirectly via insulin-like growth factor
  1. Metabolism
• prevents glucose utilization in muscles, adipose tissue, and other target tissues
• increases FFAs
• promotes amino acid uptake and protein synthesis
• overall: increases lean muscle mass, decreases adiposity, and is diabetogenic
  2. Growth
• promotes growth in size of limbs and internal organs
• linear growth at epiphyses

Question 5

Effects of IGF

Answer 5

• IGF-1 has profound effects on growth
• IGF-1 receptor has intrinsic tyrosine protein kinase activity
• insulin and IGFs probably work through different receptors.
• insulin increases the amount of IGF-1

Question 6

Regulation of GH secretion

Answer 6

1. stimulatory
   - hypoglycemia, insulin induced
   - FFA decrease
   - amino acid increase, particularly arginine
   - estrogens
   - GHRH
   - fasting or prolonged caloric restriction
   - exercise
   - stage 4 sleep
2. inhibitory
   - glucose increase
   - FFA increase
   - growth hormone, negative feedback
   - somatostatin
   - pregnancy
   - obesity

Question 7

Growth hormone excess

Answer 7

• can cause giantism if before puberty and acromegaly after puberty
• can be treated with GH analog pegvisomant that lacks one binding site and prevents dimerization of GH receptor required for activation of receptor

Question 8

Laron syndrome

Answer 8

• children resistant to GH due to mutations in GH receptor

- use of IGF-1 to treat