Endocrine Flashcards
What is the endocrine system?
collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things.
What is a hormone
A hormone is any member of a class of signaling molecules produced by glands that are transported by the circulatory system to target distant organs to regulate physiology and behaviour.
Could also act more locally as paracrine or Autocrine messengers to incite local effects
Are hormones always present?
Most are present in body fluids at all times, but in greater or lesser amounts depending on needs of the body
Paracrine vs Autocrine action
Autocrine- When hormones act locally on the same cells from which they were produced (ex- insulin inhibits further release from beta cells)
Paracrine- Acts locally on cells other then those that produced the hormone (sex steroids acting on ovary)
What are the Major organs of the Endocrine system?
Hypothalamus, pineal, pituitary, thyroid, thymus, adrenal, kidney, pancreas, ovaries, testes
Key Hormones of Hypothalamus
• Cortic0tropin releasing hormone (CRH)
-> Stimulate adrenocorticotropic hormone (ACTH) release from anterior pituitary
• Thyrotropin releasing hormone (TRH)
-> Stimulates TSH release from anterior pituitary (primarily)
• Growth Hormone Releasing hormone (GHRH)
-> Stimulates GH release from ANt. Pituitary
• Gonadotropin releasing hormone (GnRH)
-> Stim Ant. pituitary to release (LH) and FSH)
• Somatostatin
-> inhibits TSH and GH from Ant. Pituitary
• Vasopression (AKA ADH)
-> Acts on Kidney to Inc water reabsorption
Dopamine
-> Inhibit prolactin released from anterior pituitary
Key Hormones of Anterior Pituitary
• Growth Hormone (GH)
-> cell reproduction
• Adenocorticotropic (ACTH)
-> Stimulates corticosteroid (glucocorticoid and mineralcorticoid) and androgen synthesis and release from adrenocortical cells.
• Thyroid stimulating hormone
-> stimulate thyroid to release T3 and T4
• Follicle stimulating hormone
-> Stim ovaries and testes
- Lutemizing hormone- menstrual cycle, or sperm production
- Prolactin
Posterior Pituitary
- Oxitocin- stimulates contraction of uterus, milk ejection (breasts)
- Antidiuretic Hormone (AKA Vasopressin)- Inc water reabsorption by kidney
Thyroid
• Thyroid Hormone
o T3- increases metabolic rate, inc protein/bone turnover
o T4- increases responsivenbess to catecholamines necessary for fetal infant growth
Adrenal Cortex
- Glucocorticoids (cortisones) -> Is a Corticosteroids
- Mineral Corticoids (aldosterone- Increases Na absorption and K loss and H+ excretion by kidneys) ->Is a Corticosteroids
- Androgens (testosterone)
Adrenal Medulla
Adrenaline (epinephrine)
Noradrenaline (norepinephrine)
2 Basic Problems of Endocrine Pathology
• Hypersecretion- increase hormones production
• Hyposecretion decreased or no hormone production
o Inappropriate target cell response
Possible Etiology for Hypersecretion
1) Excessive trophic stimulation → inc hormones
2) Defect in the negative feedback loop∴no longer
stops/shuts off, so continuous production of hormones
3) Secretory cell tumor (tumor in gland, more cells/larger
organ) → release excess secretion of hormones
Possible Etiology from Hyposecretion
1) metb defect Es missing, inhibited
2) immune disorder Ab targeting glands and/or receptors
3) Sx/Tx for hypersectretion remove part of the organ∴ less
hormone secretion
4) Receptor defects (not enough binding)
5) No trophic stimulation → atrophy
6) Dietary deficiency eg/ iodine deficiency→ non-functional T3 and T4
Thyroid hormones
triiodothyroine T3 and thyroxine T4
NOTE The normal thyroid gland produces about 80% T4 and about 20% T3, however, T3 possesses about four times the hormone “strength” as T4.
Location and shape of the Thyroid
L: below the larynx in the anterior middle portion of the neck
S: shield-shape structure, left and right lobes composed of a large number of tiny, saclike structures called follicles
What is the function of the Thyroid
the sole fx of the thyroid is to make thyroid hormone. This hormone has an effect on nearly all tissues of the body where it inc cellular activity. The primary fx of the thyroid is to regulate the body’s metb
What stimulates the Thyroid?
What is the key element required by T
The secretion of the thyroid hormone is regulated by the hypothalamic-pituitary thyroid feedback system: Hypothalamus produces TRH→stimulates the anterior pituitary to release TSH→TSH acts on thyroid gland to produce T3 and T4
What is the key element required by Thyroid?
the process of thyroid synthesis, iodine is needed.
Two types of Goiter
Endemic and Toxic
Describe pathology of an Endemic Goiter
need iodine to form hormone… iodine deficiency d/t lack of iodine in diet→dec production of T3 and T4 → compensatory inc in TSH to create more T3 and T4 →hyperplasia in the thyroid inc in size and number d/t inc of TSH, making lots of un functional T3 and T4.
- > Too much TSH causing too much load on the cells
- > cells spread/grow and divide→goiter
What causes a toxic Goiter?
there is excess production of thyroid hormones from functionally autonomous thyroid nodules, which do not require stimulation from thyroid stimulating hormone (TSH)
toxicity from inc levels of hormone d/t hyperactivity. End result is a large nodular gland
Describe Hyperthyroidism and the clinical presentation
AKA Grave’s Disease
mostly auto immune
is the clinical syndrome that results when tissues are exposed to high levels of circulating thyroid hormone.
- most common Hyperthyroidism 80-90%,
- most often seen in young women
- If you see the following 3 things, they indicate
Graves disease:
1) hyperthyoidism
2) goiter
3) exopthalmus protruding eyeballs, fluid deposits in fat pads and protruding eyeballs
Pathology of Graves Disease
AKA hyperthyroidism
TSAb Thyroid Stimulating Ab mimics TSH and binds to Thyroid receptors → stimulates T3 and T4, but stays there and doesn’t disassociate normally d/t inability of Es to breakdown the structure of the TSAb. RESULT= lots of T3 and T4
- Body compensates negative feedback by dec TSH → test shows elevated T3 and T4 and low TSH