Intro to Endocrine Flashcards
What is the goal of the endocrine system?
Homeostatic regulation of physiological processes through coordinated function of the endocrine and autonomic nervous system. Critical for metabolism, reproduction, and growth. Has behavioral components
What coordinates components of the endocrine system?
Hypothalamus
What does endocrine mean?
Secrete internally, usually into systemic circulation
What is a hormone?
Chemical substance produced by a gland or tissue that acts upon distant targets at low concentrations. Targets must have receptors
What are the functions of a hormone?
- Reproduction and sexual differentiation
- Development and growth
- Maintenance of the internal environment
- Regulation of metabolism and nutrient supply
What is a permissive effect?
One hormone may have an effect on another hormone. to reach it’s physiological max
How do you get integrated activity of the endocrine and nervous system?
- Endocrine reflex loop
- Autonomic reflex loop
- Regulatory behavior
What is the endocrine reflex loop?
- Stimulus from afferent nerves
- Central integration (hypothalamus)
- Release hormone
- Hormone action upon target
- generally negative feedback loop
What are the types of hormones?
- Metabolism
- Growth
- Reproduction
What are the types of metabolism hormones?
- M-energy
- M-Mineral
What are the M-energy hormones?
Insulin, glucagon, cortisol, epinephrine, thyroid hormone, growth hormone
What are the M-mineral hormones?
Parathyroid hormone, calcitonin, angiotensin, renin, aldosterone
What are the growth hormones?
Growth hormone, thyroid hormone, insulin, estrogen, androgens, Growth factors
What are reproduction hormones?
-Estrogen, androgen, progesterone, LH, Follicle-stimulating hormone, prolactin, oxytocin
What are the different chemical composition of hormones?
- Proteins
- Peptides
- Amines
- Thyroid hormone
- Steroids
Which hormones are proteins?
- Growth hormone
- Insulin
- Corticotropin
How are protein hormones made?
Synthesized as prehormones and modified to prohormones. They are stored within granules in the gland until released via exocytosis
Which hormones are peptides?
- oxytocin
- Vasopressin
- Angiotensin II
- Cholecystokinin
Which hormones are amines?
- Dopamine
- Nor/Epinephrine
- Melatonin
Which hormones are steroids?
- Adrenocortical
- Sex hormones
How are steroid hormones made?
Synthesized from cholesterol in the liver and they are released as they are made
What percentage of hormones are proteins and peptides?
85%
Where are protein receptors?
Cell membrane. Proteins are water soluble so they don’t cross the membrane
Why can’t you administer peptide hormones orally?
They are easily digested and inactivated by gastrointestinal enzymes
What percentage of hormones are steroid hormones?
15%
Where are steroid hormone receptors?
Cytoplasmic receptors. Steroids have hormone-receptor complex traffic to nucleus
Can you administer steroid hormones orally?
Yes
Amino acid and fatty acid derived hormones are derived from what?
Tyrosine or tryptophan
The adrenal medulla produces?
Catecholamines (Nor/Epinephrine)
What produces melatonin?
Pineal gland
What is an intracrine system?
Goes within cell, not a hormone, usually second messenger signaling
What is the paracrine system?
Released and goes to neighboring cell. If it enters blood cell ->local hormone
What are autonomic reflex loops?
This is an integration of ANS and endocrine
What is the result of Cushing’s Syndrome?
Increased secretion of cortisol, does not tell us where the problem is originated
Cushing’s disease is characterized by what?
- Primary locus: adrenal tumor causes excess cortisol release by tumor
- Secondary locus: pituitary tumor adenoma causes excess ACTH-> secondary excess cortisol
What are some amino acid derived hormones?
- Catecholamines
- Thyroid hormones
- Melatonin
What are hormones derived form fatty acids?
Eicosanoids
- Prostaglandins
- Thromboxanes
- Leukotrienes
What inhibits eicosanoids?
NSAIDs
Can hormones derived from amino acids be administered orally?
Yes
How do you transport protein and peptide hormones?
They are hydrophilic so they can be dissolved in plasma
How do you transport steroid and thyroid hormones?
These are lipophilic and are not soluble in water. They require carrier proteins with either specific binding proteins or non-specific binding proteins
How do peptide or protein hormones interact with cells?
- Specific receptors on membranes
- Second messenger systems
How do steroid hormones interact with cells?
- Specific receptors in cytoplasm (type I nuclear receptors)
- Hormone/receptor complex translocate to nucleus
- Complex binds DNA and effects gene transcription
- Affects mRNA synthesis and protein synthesis
What is the purpose of second messenger systems?
Signal amplification
Where are receptors for thyroid hormone?
Nuclear receptors (type II)
How are protein/peptide hormones metabolized?
- Enzymatically cleaved
- Metabolite is less biologically potent
- short half life
How are steroids metabolized?
- Reduction of molecules
- Conjugation with sulfates and glucoronides in liver
- Excreted in urine
- Can get metabolism to more active form of steroid
- Longer half life
What does hormone response depend on?
- Overall amount
- Permissive effect
- Sensitivity
- Hormesis
Which type of hormone has relatively fast actions?
Protein or peptide hormones
Which type of hormone has relatively slow actions?
Steroid hormones
What is the relationship between bound and free hormone?
These are proportionate so an effect on one has an effect on the other. Needs to be free to bind to receptor
What is needed for the release of stored Peptide, protein, or catecholamine hormones?
Calcium and ATP in the cell
What are the binding proteins for thyroid hormone?
- Thyroxine binding globulin
- Transthyretin
- Albumin
What is a steroid carrier protein?
Transcortin and albumin
Steroid receptors bind to what on the DNA?
Palindromic hormone response element
Type II nuclear receptors bind to what on the DNA?
Direct repeat hormone response element
What is an exogenous hormone?
Comes from outside of the body. Hormone therapy
What can effect exogenous hormones?
- Type of tissue
- Time of observation
- Species, age, sex
- Type of hormone, formulation, and how delivered
- Pattern of release or time of day
- Dose-effect relationship
What is hormesis?
U shaped dose response curve where a low dose has physiological effect, but a high dose is inhibitory or pathophysiologic responses
How do you control hormone secretion?
Negative feedback loops generally
What parts of the brain regulate circadian rhythms?
Suprachiasmatic nucleus
Pineal body
When do cortisol levels peak?
After you wake up and eat is the first largest peak. and smaller peaks after subsequent meals
What is the most common endocrine disorder that affects cats?
Hyperthyroidism
What are some ways the endocrine system can fail?
- Loss of hormone production
- Normal hormone release but apparent loss of function
- Excess hormone
What is an iatrogenic hormone disorders?
Disease caused by veterinarian’s intervention
What are some examples of iatrogenic hormone disorders?
- Hyperadrenocarticism- overuse of glucocorticoids
- hypoadrenocorticism from adrenalectomy
- Hypothyroidism from goiter treatment
- Pan-pituitary hormone loss resulting from hypophysectomy
What system responds quicker and is more localized?
Nervous system
Which system bathes all cells with hormones and may take longer to see response?
Endocrine system
What neurohormones are released in the pituitary gland ?
Oxytocin and Vasopressin
What releasing factors that control anterior pituitary gland (adenohypophysis) are released from hypothalamus?
- CRH
- GHRH
- TRH
- GHIH (somatostatin)
- PRF
- PIF
- GnRH
- LHRH
What is a stress response homone?
Corticotropin-releasing hormone is released at the base of hypothalamus at the medium eminence this goes to the adenohypophysis and it releases ACTH and get release of cortisol
What are the three main parts of the pituitary?
- Adenohypophysis (anterior pituitary, Pars Distalis)
- Neurohypophysis (posterior
pituitary, Pars Nervosa) - Pars Intermedia (intermediate lobe)
What is Rathke’s pouch?
Oral ectoderm forms pars distalis and part of pars intermedia (can get endocrine disorders if this doesn’t form correct)
What forms the infundibulum and pars nervosa (pp)?
Neuroectoderm
What is the medium eminence?
Fenestrated capillary bed where hypothalamic releasing factors are released to enter the pituitary gland
What is the pituitary fossa?
Concave portion of the skull where the pituitary sits and the hypophyseal stalk is at the top of this fossa and could be damaged there if head is hit hard enough
What could be a side effect from pituitary tumors?
Could get visual problems because tumor travels up the infundibulum and affect the optic chiasm
Signs vs symptoms
Signs-what you see
Symptoms- what they tell you
What are the acidophils?
Somatotropes and lactotropes
What are the basophils?
- Thyrotropes
- Gonadotropes
- Corticotropes
What are pituicytes?
Support cells in the posterior pituitary. Cover terminal when not active, when it is active it unblocks the terminal so it can release hormone
