Always in motion is the future.

Week 6: Endocrine/Reproductive

Pituitary

Updated by Tracey 16 August 02

The pituitary/hypophysis is a tiny gland under the hypothalamus at the base of the skull. Blood supply passes through the hypothalamus carries secretions from the hypothalamus to the pituitary, controlling many pituitary secretions. Secretory cell types in the ant. pituitary are typically specialized to the substance they secrete (FSH and LH are both secreted by the same cell type). The pituitary is divided into two parts...

Anterior (adenohypophysis): hormones control metabolic functions, and except in the case of growth hormone, stimulate specific target glands.
- Growthsomatotropic hormone (somatropin) enhances protein formation, cell multiplication and differentiation to promote growth in all body cells.
- Adrenocorticotropin controls secretion of some adrenocortical hormones affecting glucose, protein and fat metabolism.
- Thyroid-stimulating hormone (TSH) controls thyroxine secretion by the thyroid, which controls chemical reaction rates in most cells in the body.
- Prolactin promotes mammary gland development and milk production.
- Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) control growth of gonads and their hormonal and reproductive activities.
Posterior (neurohypophysis): secretes antidiuretic hormone to control water excretion into urine to control water concentration in body fluids -- controlled by osmotic (fluid) pressures and blood volume; oxytocin contracts breast alveoli to help deliver milk from glands to nipples during suckline and contracts uterus aiding baby delivery at end of gestation.

Growth Hormone

Promotes growth in tissues capable of growing through size and mitosis. Also increases protein synthesis rates, increases fatty acid mobilization and utilization, decreases use of glucose. Glucose storage is also promoted until cells reach saturation, after which blood glucose can rise if GH levels are extremely high. GH probably stimulates somatomedin production in liver, which illicites changes, therefore, only minute amounts of GH are needed. GH secretion varies based on nutritional or stress status (starvation, trauma, excitement, hypoglycemia, exercise). Cell protein levels primary primary control factor of GH secretion, blood glucose can also effect.

Protein deposition most likely result of: enhanced aa transport through cell membranes, increasing aa concentration in cells; enhanced protein synthesis by ribosomes; stimulate transcription resulting in increased mRNA formation; decrease in intracellular protein breakdown (catabolism) and utilization of protein and aa's for energy, likely due to ffa mobilization.

GH abnormalities: dwarfism -- secretion deficiency during childhood, development decreased; giantism -- cell tumors in the gland produce excessive amounts of gh, resulting in rapid growth, can be fatal if tumor destroys gland; acromegaly -- post-adolescent tumor results in growth of soft tissues and in bone thickness (not length, since epiphyses are closed), typical signs include forward slant of forehead, development of supraorbital ridges, increased nose size, large feet, protruding jaw, hunched back, greatly enlarged soft tissue organs (tongue, liver, kidneys).