Anterior Pituitary Gland Flashcards
(34 cards)
Communication with hypothalamus
Only vascular
No tissue connection between hypothalamus and anterior pituitary
Control Regulation
Control regulated by hormones that will arrive via hypophyseal portal system
Releasing Hormones General
Made by hypothalamus
Target anterior pituitary gland
cause it to produce/release another hormone into systemic circulation (tropic effects)
Stimulating Hormones General
Made by anterior pituitary gland
target cells/organs in the peripheral body
cause some targets to produce/release another hormone and others have non-endocrine effects in other targets (tropic and non tropic effects)
Cell Population of Anterior Pituitary
Six separate populations of cells (6 types of releasing/stimulating hormones)
All individual cell have a receptor for a specific releasing hormone from hypothalamus and the machinery to make one type of stimulating hormone (each releasing hormone has 1 specific stimulating hormone)
Some cells also have receptors for a specific inhibiting hormone made by the hypothalamus (GH and prolactin)
Anterior Pituitary Function vs. Posterior
Anterior pituitary gland MAKES and releases hormones
Posterior pituitary gland stores hormones that were made in the hypothalamus
Anterior Pit. Hormones General
All are peptides
and all are stimulating hormones
2 Functional Groups of Anterior Pit. Hormones
- Those targeting non-endocrine targets (non tropic)- certain aspects of growth (body in general) and mammary gland/milk production
- Those targeting endocrine targets (tropic)- adrenal cortices (glucocorticoids), thyroid gland (thyroid hormones), gonads (sex hormones), and skeletal muscle/liver (for growth)
Anterior Pituitary Hormones
All are stimulating hormones Non-tropic: 1. Growth hormone (GH) 2. Prolactin Tropic: 3. Corticotropin (CTH or ACTH) 4. Thyroid Stimulating Hormone (TSH) 5. Follicle- Stimulating Hormone (FSH) 6. Leutinizing hormone (LH) (1. Growth Hormone)
Growth Hormone Terminology
Somatotropin (ST)= Growth Hormone (GH) from anterior pituitary
Somatostatin (SS)= Growth Hormone Inhibiting Hormone (GHIH) from hypothalamus
Somatomedins (S’Md)= Insulin Like Growth Factors (IGF’s) from tissues
IGF’s
Insuling like growth factors (or somatomedins)
Peptides that promote growth
Multiple types made by several tissues which cause the direct growth of cells
Metabolic effects of growth hormone
(Non growth related effects)
Mobilize fat stores as primary energy source so we don’t use proteins/carbohydrates so we can save muscle and glucose (brain can only use glucose)
Growth related effects of growth hormone
Primary direct effect of GH on target tissue= release of somatomedins (not bodily growth)
Somatomedins (IGF’s)
A group of GH/ST related growth factors made mainly by the liver (but also other tissues)
These are the cells which actually cause bodily growth (bone, cartilage and muscle)
Travel through systemic circulation and increase linear growth (height), lean body mass, organ size/function
Mediate protein, fat, CHO, Ca, PO4 metabolism
Difference between Somatomedins and Growth Hormone in body
Toy Poodles= Small amount of S’md
Mini Poodles= Medium amount of S’md
Standard Poodle= Large amount of S’md
All 3 have same amount of GH but liver doesn’t respond as vigorously with S’mds in the smaller breeds
Regulation of GH- promote secretion
Hypothalamus integrates bodily signals then releases GHRH which goes (via hypophyseal portal system) to anterior pituitary
Ant. Pit responds to GHRH by releasing GH
GH travels to target tissues via systemic circulation to target tissues and trigger somatomedins which are released and act
Regulation of GH- Inhibit Secretion
Long loop negative feedback presumably caused by secretion of GHIH from hypothalamus
Increased GH and/or somatomedin blood levels communicate back to hypothalamus and caused reduced GH release
Regulation of somatomedin- promote secretion
GH/ST arrival at target tissues causes release of SM
Regulation of somatomedin- inhibit secretion
Negative feedback loop
Both GH and SM’s inhibit secretion by anterior pit.
With the loss of GH, SM secretion decreases
Prolactin
Non- Tropic
Targets mammary gland
Induces and maintains milk PRODUCTION
Regulation of prolactin
Negative feedback (involves dopamine)
PIH- Prolactin inhibiting hormone
Involves inhibition or loss of inhibition
Corticotropin
(CH) aka Adrenocorticotropin (ACTH)
Tropic
Targets adrenal cortex
Corticotropin function
Stimulates adrenal cortical growth and activity
Increases plasma levels of corticosteroids
ACTH and melanocyte stimulating hormone
ACTH contains the amino acid structure of MSH
Skin darkening is one clinical sign of conditions having HIGH plasma ACTH (ex. addisons)
