Flashcards in Pituitary Gland Deck (38):
Where is the pituitary gland located?
1. Small oval gland that lies within sella turcica
2. Hangs down inferior to hypothalamus
3. Connected to hypothalamus by the infundibulum
How is the pituitary gland divided?
1. Divided into two lobes based on the function & developmental anatomy
A. Anterior lobe (Adenohypophysis)
B. Posterior lobe (Neurohypophysis)
What hormones does the anterior pituitary gland secrete? What organs/glands do these hormones affect?
1. TSH: thyroid
2. ACTH: adrenal cortex
3. FSH, LH: Testes, ovaries
4. Growth hormone: entire body
5. Prolactin: mammary glands
6. Endorphins: pain receptors in the brain
How is the anterior pituitary gland controlled?
Anterior pituitary gland is controlled by regulatory hormones secreted by the hypothalamus
How do the hormones that control the ant. pit get there?
1. Hormones reach the anterior pituitary via hypothalamo- hypophyseal portal system
A. Takes venous blood carrying regulatory hormones from hypothalamus directly to the anterior pituitary
What hormones are secreted by the posterior pit gland?
Where are ADH and Oxytocin made?
Specialized Neurosecretory cells in the hypothalamus
What hormones control the secretion of ant pit hormones?
1. Thyrotropin Releasing Hormone (TRH)
2. Corticotropin Releasing Hormone (CRH)
3. GHRH & GHIH
A. Growth Hormone Releasing Hormone (GHRH) - Somatotropin
B. Growth Hormone Inhibitory Hormone (GHIH) - Somatastain
4. Gonadotropin Releasing Hormone (GnRH)
5. PIH & PRH
A. Prolactin Inhibitory Hormone (PIH)
B. Prolactin Releasing Hormone (PRH)
How many hormones are released by the ant pit?
6 peptide hormones
What is the function of TSH?
1. Thyrotropin Stimulating Hormone (TSH)
2. Stimulates thyroid gland to secrete thyroxine & triiodothyronine
A. As T4 & T3 increase, TRH & TSH decrease
What is the function of ACTH?
1. Adrenocorticotropic Hormone (ACTH)
2. Stimulates release steroid hormones from adrenal cortex
A. Glucocorticoids & mineralcorticoids
3. Affects metabolism of glucose, proteins, fats
4. Affects immune system & inflammation
5. As cortisol levels increase, CRH & ACTH decrease
What are the main functions of the growth hormones?
1. Stimulates cell growth & replication by accelerating rate of protein synthesis
2. Increases mobilization of fatty acids from adipose tissue & use for energy
3. Controlled by hypothalamus via releasing or inhibiting hormones
What are the direct effects of GH?
1. Salt retention
2. Decreased insulin sensitivity
4. Protein synthesis
5. Epiphysial growth
6. Stimulates IGF-1: insulin like growth hormone 1
What are the indirect effects of GH (through IGF-1)?
1. Insulin-like activity
2. Antilipolytic activity
3. Protein synthesis
4. Epiphysial growth
What is the major controller of GH secretion?
1. Long term state of protein nutrition
A. If protein stores low, GHRH increases, leading to increase GH
What is the general function of LH?
1. Onset ovulation
2. Stimulates corpus luteum
3. Stimulates release of progesterone
What is the general function of FSH?
1. Regulates development of follicle
2. Stimulates release of estrogen
What are the general functions of prolactin?
1. Stimulates mammary gland development
2. Stimulates milk production in mammary glands during pregnancy & post partum
What is the general function of MSH?
1. Darkens skin
2. Endocrine functions unclear
What is the general function of oxytocin?
1. Influences activity of female reproductive system
2. Released at end of gestation
3. Causes uterine contractions
4. Milk ejection reflex during lactation
What are the functions of ADH?
1. Inhibits formation of urine
2. Reduces water excretion
What conditions are caused by growth hormone excess?
What is the pathophys of acromegaly?
1. GH excess that begins after epiphyseal closure
2. Pituitary adenoma
What are the sxs of acromegaly?
1. Especially notable in hands, feet, face
2. Many soft tissue organs also become greatly enlarged
A. Tongue, liver, kidneys
3. Increased growth of bone, cartilage and other tissues
A. Increased bone density and width
B. Proliferation of connective and soft tissues
4. Increased CHO catabolism
5. Increased protein synthesis
What is the pathphys of gigantism?
1. GH excess that is present in childhood, before closure of epiphyseal plates of long bones
What other effects may be present from a pituitary adenoma?
1. Large tumors cause destruction of the pituitary and deficiency of other pituitary hormones and may affect the optic chiasm and vision
A. Bilateral hemianopsia
What are the sxs of gigantism?
1. Increased growth of bone, cartilage and other tissues
A. Remarkable height increases up to 6 inches/yr
Causes enlargement of internal organs
2. Increased CHO catabolism
3. Increased protein synthesis
What is the pathophys of dwarfism?
1. GH deficiency during childhood
2. Features of body develop in appropriate proportion to each other, but rate of development is decreased
What are the sxs of dwarfism?
1. Short stature
2. Delayed growth
3. Delayed puberty
4. May respond to exogenous GH
What is the general pathophys of diabetes insipidus?
1. Insufficiency ADH causes immediate excretion of large volumes of dilute urine
2. Plasma hyperosmolarity results
What is the neurogenic etiology of DI?
lesion of hypothalamus (thirst center), infundibulum or post pituitary blocks ADH synthesis, transport or release
What is the nephrogenic etiology of DI?
Generally related to disorders or drugs that damage renal tubules
What are the sxs of DI?
1. Intense thirst
2. Craving water
3. Large volume polyuria
A. 3-18 l/day
What are the dx studies for DI?
1. No single lab test can confirm DI
3. BUN, Cr
4. Na, K
5. Ur Specific Gravity
A. < 1.006
6. 24 hr urine
A. Vol, Gluc, C
What is the treatment for central DI?
A. Treatment of choice
B. Antidiuretic effect
C. Binds to V2 receptor
D. Increases water permeability and
reabsorption in collecting tubules
What is the treatment for nephrogenic DI?
A. MOA unknown
What are changes in GnRH and FSH controlled by?
circulating levels estrogen and inhibin