Anterior Pituitary Hormones Flashcards
What is the role of somatotropin/GH?
Bone and Muscle Growth
Where is GH produced?
By somatotrophs in the anterior pituitary gland
GH is structurally similar to …
… prolactin
What is IGF-1?
Molecules secreted in response to GH which mediate actions and regulation of GH
What class of molecules are IGF-1?
Somatomedins
What molecule is IGF-1 structurally similar to?
Insulin
Is GH or IGF-1 measured for assessing GH deficiency?
IGF-1 is measured since they do not fluctuate through the day
Which cells are signalled to grow after IGF-1 secretion?
Cells with adequate nutrients undergo hyperplasia and hypertrophy
What effect do IGF-1 and GH have on bone growth in children?
Stimulate linear bone growth at the epiphyseal plate
How do IGF-1 and GH affect muscle growth?
Stimulate myocyte hypertrophy
Increase protein synthesis
What effect do GH and IGF-1 have on blood glucose concentrations?
Increase serum glucose
How do GH and IGF-1 increase serum glucose concentration?
Increase hepatic gluconeogenesis
Increase lipolysis and lipid oxidation
Antagonize the action of insulin
What factors may increase GH levels?
Sleep
Hypoglycemia
Stress
Increased ghrelin levels
What factors may decrease GH levels?
Aging
Obesity
Glucose
What is dwarfism?
Generalized deficiency of anterior pituitary hormone secretion
What is a characteristic of dwarfism during puberty?
Does not reach puberty due to gonadotropin deficiency
What are potential causes of dwarfism?
GH deficiency
Inability to form somatomedin C
What is gigantism?
Excess GH secretion before puberty
What is a potential cause of gigantism?
Tumors in anterior pituitary at GH secreting centers
What are potential side-effects of gigantism?
Hyperglycemia
What is acromegaly?
Excess GH after puberty
Because GH is secreted after puberty, the person cannot grow taller
What are the signs of acromegaly?
Bones of hands, feet, cranium, supra orbital ridges, nose, vertebrae, jaw grow
Kidney, lungs and tongue increase in size
Kyphosis (Hunching of the back) is caused by increased growth of vertebrae
Functions of prolactin
Milk production + Mammary Gland Development
Enhances maternal nurturing behaviours (cuddling, protection, grooming)
Reproduction
Nerve Formation
Fetal Development
Where is prolactin produced?
Lactotrophs in the anterior pituitary gland
Also produced at extra-pituitary sites
Which tissues are affected by prolactin?
Breast
Pituitary
Indirect influence of gonads
What impact does prolactin have on sex hormones?
Depresses sex hormones (estrogen and testosterone)
Relation between prolactin and autoimmunity
Prolactin suppresses negative selection of B cells
Makes immune system more likely to attack native cells
Causes higher incidence of autoimmune diseases in childbearing age women and postpartum women
Positive regulators of prolactin secretion
Nipple stimulation
Estrogen
Thyrotropin-releasing hormone
Negative regulators of prolactin secretion
Dopamine
Progesterone
How does prolactin level effect sex hormone production?
Prolactin inhibits GnRH production
GnRH production inhibits LH and FSH secretion
How does dopamine reduce prolactin secretion?
Prolactin increases dopamine production in hypothalamus
Dopamine inhibits prolactin
How does progesterone reduce prolactin secretion?
Inhibits prolactin at level of peripheral receptor
