Introduction to Endocrinology Flashcards
Basic Endocrinology Control
Negative Feedback mechanism
Half-life
Hormone imbalances
Negative feedback mechanism Control
(Exception is reproductive hormones)
As level of circulating hormone falls, stimulus is turned on
As level of circulating hormone rises, stimulus is turned off
Half-life Control
Amount of time it takes for 1/2 of the hormone to be cleared from the body
Longer half-lives
Steroids - hours
Short half-lives
Protein horomones - minutes
Hormone Imbalance Control
Hyper-production
Hypo-production
Types of Hormones
Protein
Steroids
Protein Hormones examples
Amino acids
Poly-peptides
- small chains, Catecholamines, Thyroid hormones
Steriod Hormones examples
Stimulating hormones, insulin, PTH, Calcitonin, ADH, Glucagon
Hypothalamus
Master Gland
Connected to pituitary gland
Contains neurosecretory cells that produce “releasing factors” which act on pituitary gland
Examples of Hypothalamus Releasing Factors
Thyrotropin Releasing Factor (TRH)
Adrenal cortical Releasing Factor (ACRH)
Gonadotropin Releasing Factor (GTRF)
Pineal Gland
Produces melatonin from serotonin
- Role in “good sleep”
Complete function unknown
Pituitary Gland
Has two lobes
- Anterior
- Posterior
Hormones of the Anterior Pituitary
Stimulating Hormones
TSH, ACTH, FSH/LH (released by posterior)
Growth Hormone
Prolactin
Example of Releasing and Stimulating Factors
Thyroid Gland
TRH, TSH
Act on principle of negative feedback
TRH
Thyroid Releasing Hormone
Hypothalamus
TSH
Thyroid Stimulating Hormone
Pituitary
Growth Hormone Direct Effects
Stimulates fat cells to break down triglycerides
Stimulates protein anabolism
Anti-insulin activity which results in increased glucose in blood
Growth Hormone Indirect Effects
Acts on liver to produce insulin-like growth factor-I (IGF-I)
IGF-I
Stimulates growth of longitudinal bones
Growth Hormone Inhibited
Somatostatin
Peptide hormone which inhibits the release of GH
Growth Hormone Abnormalities
Overproduction - Pituitary Tumor
- Before puberty: Giantism
- After puberty: ACromegaly
Giantism Info
Rare
Excessive secretion of GH occurs during childhood before bone plate closures
Giantism Results
Overgrowth of long bones and very tall stature
Height is accompanied by growth in muscles
Bone deformities can develop
Disorder can delay puberty
Acromegaly Info
Changes are best seen in photographs or dental records over time
Caused by pituitary tumor which forms after puberty (Adenoma)
Physical symptoms occur because of epiphysis plates are closed
Acromegaly Causes
Overgrowth of bone in skull and mandible
Coarsening of facial features
Intra-dental separations
Broadening of the hands and feet
This occurs over many years (~15 to 20)
Pituitary Dwarfism
Deficiency of GH
Individual is perfectly proportioned but of short stature
Children can be treated with GH injections