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
Prolactin
Normally associated with milk production
Tumors with Prolactin
Cause milk production in men and non-nursing women
Hormones of the Posterior Pituitary
Oxytocin
Vasopression or Anti-Diuretic Hormone (ADH)
Oxytocin
Acts on Cervix/Uterus - causes uterine contractions
Nipples - causes milk ejection
Relationship hormone
Vasopression or ADH
Osmoreceptors/volume receptors
Increase permeability of collecting ducts to H2O
Vasoconstriction
Maintains Blood osmolality
Turned on when blood osmolality rises - stimulates thirst
ADH Deficiency
Diabetes insipidis - increase in thirst as collecting ducts are not permeable
Blood Osmolality is increased
Urine Osmolality is decreased
Due to inability of kidneys to reabsorb water in absence of ADH
Syndrome of Inappropriate ADH (SIADH)
Excessive ADH secreation usually secondary to pituitary tumor
Decreased Blood Osmolality
Increased Urine Osmolality
Adrenal Gland Location
On top of each kidney
Adrenal Gland Zones
Adrenal Cortex
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
Adrenal Medulla
Adrenal Cortex Hormone Classification
Steroids
Zona glomerulosa Hormone
Aldosterone
Zona fasciculata Hormone
Cortisol
Zona reticularis
Androgens and Estrogens (Testosterone and Estrogen)
Adrenal Medulla Hormones
Fight or Flight
Epinephrine
Norepinephrine
Production of Hormones of Adrenal Cortex
Manufactured from a cholesterol precursor
Control is under action of various enzymes
Disease states associated with loss of or altered enzyme function in pathway of hormone production
Zona glomerulosa location
Outermost zone - just below the adrenal capsule
Zone glomerulosa Secretion
Mineralocorticoids
- Involved in regulation of electrolytes in ECF
- Aldosterone is the most important hormone
Organs Required for Aldosterone
Liver
Kidney
Lungs
Adrenals
Zona fasciculata Location
Middle zone - between the glomerulosa and reticularis
Zona fasciculata Secretion
Glucocorticoids
- Major one is cortisol
Glucocorticoids increase blood glucose levels
Effects protein and fat metabolism
Zona reticularis Location
Inner zone of the adrenal cortex
Zona reticularis Secretions
Reproductive steroids to account for primary sexual development (Estrogen & Testosterone)
Puberty - gonads produce additional sex steroids which accounts for development of secondary sexual characteristics
Syndrome vs Disease of Adrenal Cortex
Pituitary disease
Adrenal tumor
Exogenous cortisol (syndrome)
Results: Increase in blood glucose, aldosterone, reproductive hormones
Disease/Syndromes of the Adrenal Cortex
Cushing’s
Addison’s
Superficial Characteristics of Cushing’s
Moon face
- Edematous appearance of face
- Acne & hirsutism (excessive facial hair growth)
Buffalo torso
- Redistribution of fat from lower parts of body to thoracic and upper abdominal areas
Cushing’s Affect on Carbohydrate Metabolism
Adrenal Diabetes or Diabetes Mellitus
Hypersecretion of cortisol results in increase blood glucose levels (Up to 2x normal)
Prolonged oversecretion of insulin can “burn out” beta cells of pancreas
Cushing’s Affect on Protein Metabolism
Decrease protein content in most parts of body resulting in muscle weakness
Lymphoid tissue - decrease protein synthesis suppresses immune system
Lack of protein deposition in bones results in osteoporosis
Collagen fibers of subcutaneous tear forming striae
Overall Signs and Symptoms of Cushing’s
Increased Cortisol levels with NO diurnal variation
Moon Face
Striae
Buffalo Hump
High blood pressure
Hyperglycemia
Increased Na+ levels
Decreased K+ levels
Acidosis
Females may demonstrate signs of masculinization
Addison’s disease Caused by
Low levels of pituitary hormone usually from immune destruction of adrenals or via secondary to infection
Addison’s Signs and Symptoms
Very thin
Hypoglycemia
Decreased blood pressure
Decreased Na+ levels
Increased K+ levels
Acidosis
Skin and mucus membranes may darken from release of melanocyte inhibiting factor (MIF)
Other Disorders of Adrenal Cortex
Primary Hypoaldosteronism
Primary Hyperaldosteronism
Primary Hypoaldosteronism
May occur separate from Addison’s Disease
- Rarely found at birth causing inability to reabsorb Na+ and loss of blood pressure (death in newborn)
Primary Hyperaldosteronism
Conn’s disease
Presents with hypertension, muscle weakness, polyuria, and polydipsia
Adrenal Medullary Hormones
Catecholamines
- Epinephrine
- Norepinephrine
- Dopamine
Adrenal Medullary Hormones Info
Act as neurotransmitters
Dopamine manufactured from Tyrosine
Norepinephrine and Epinephrine manufactured from Dopamine
Adrenal Medulla Disease States
Tumors of the adrenal medulla
- Considered neurological in nature
Neuroblastoma
Pheochromocytoma
Neuroblastoma Info
Undifferentiated neural tumor
Rare
Found in newborns
Originate from adrenal medullary cells
Presents as large abdominal mass
Incompatible with life
Neuroblastoma Laboratory Diagnosis
Tumor increased production of dopa (dopamine precursor)
All 3 catecholamines are elevated (Dopamine, Epine, Norepine)
Both liver metabolites elevated (VMA and HVA found in urine)
Pheochromocytoma General Info
Well differentiated neural cells
Found in adults
Pheochromocytoma Clinical Presentation
High blood pressure
Increased respiration rate
Increased heart rate
Sweating
Anxiousness and Nervousness
Pheochromocytoma Laboratory Results
Norepinephrine Increased
Epinephrine Increased
Dopamine Normal
Liver Metabolites:
- Normetanephine Increased
- Metanephrine - Increased
VMA increased in urine
No elevation in HVA as dopamine is normal
