Chapter 25: Hormones & Endocrine System,  Kimball,  Farabee,  Wiki,  cute: Ch 25
always hard to beat figures in chapter Medical Biochemistry Resource

1) Biology and Society:
2e: Of Hunger & Hormones: ghrelin is new, no questions on it
1e: Menopause cause & symptoms, and risks of hormone replacement therapy, p 545,  .gov

2) Hormones (H): Overview, hormones are like emails they are messages from one cell to another
Each H is secreted by a gland! (but more tissues than these secrete hormones, remember?),
& targets one or more cell type(s) anywhere in the body, fig 2
Target cells have H specific receptor proteins.
The action each H has depends both on the specific H & the specific type of target cell

H Chemistry: most are water soluble: catecholamines or peptides e.g. ADH or proteins e.g. insulin;
But 5 types (6 with vitamin D, scroll to synthetics) are steroids which, with thyroxine, are lipid soluble

2. If H is H2O soluble, receptor protein is on cell surface, fig 3, anim (scroll), 
3. If H is lipid soluble, fig 4, thyroxine + steroids: 1) estrogen, 2) progestin, 3) androgen,
   
4. 4) mineralocorticoid (conserves salt), & 5) glucocorticoid (stress hormone, raises blood sugar)
5. these enter target cell(s), each type find its receptor in the cytoplasm, & changes gene(s) activity
   
6. Thyroid (gland): wiki: molecule is lipid soluble
   

 Comparative endocrinology? = all animals, but not in CH (p 556: dog secreting prolactin!)

CHECKPOINT p 547
1. How does a hormone get from its source to its target cells?
2. What are the major differences between peptide/protein H & steroid H?
3. How can epinephrine (pseudoephedrine) be both a bronchodilator & a vasoconstrictor

3) Human Endocrine System Kimball fig, Farabee, List of glands,

2. Endocrine glands/hormones: fig 5 & Table 1: from brain to gonads:
3. hypothalamus/pituitary, pineal, thyroid, parathyroid, (thymus, heart, guts), pancreas, adrenals, (kidneys), gonads 

All H work to maintain homeostasis = ~ constancy of the internal environment, so
the actions of each hormone include an effect which decreases its secretion!
E.g. more insulin is secreted when blood sugar rises, but insulin's actions lower blood sugar

4) Hypothalamus & Pituitary, p 549, fig 6
The BRAIN has input from all the body's receptors, so IT knows the status of homeostasis,
So the secretion of many H is determined by the brain,
Primarily by the hypothalamus working through the anterior & posterior pituitary

    Hypothalamus produces, but posterior pituitary secretes, two H:
1) Anti-diuretic H or vasopressin (raises BP) > reduces water excreted by kidneys, fig 7
NOTE: secretion is in response to dehydration > rising osmolarity or body fluids
2) Oxytocin: stimulates labor contractions, & also milk let down in response to suckling
NOTE: secretion is reflex response to cervical stretch, or suckling

   Hypothalamus controls 6 anterior pituitary (AP) hormones
Do four here, two more down page @ thyroid & adrenal.
The pattern: is a chain of 2 or 3 hormones, (portal) blood: goes from Hypothalamus to AP, resource
Hypothalamus releasing hormone (RH) > 2) anterior pituitary hormone > 3) target &/or gland > gland hormone
Gonadotropin RH > AP > two gonadotropins: FSH & LH > gonads > produce egg/sperm & sex steroids
       Prolactin RH > AP > prolactin                                 > breast > milk production & secretion
     Growth H RH > AP > growth H                                > growth (pre-puberty), fig 8

H/AP also secretes endorphins: in response to exercise & other stimuli: runners high, natural painkiller

CHECKPOINT not in textbook
A bump on the head may stop the secretion of a hypothalamic or pituitary H.  Predict effect:
1) No ADH secretion >
2) No growth H RH: a) in adult >              b) in child >
3) No Gonadotropin RH secretion >
Post-menopause: does secretion of FSH & LH rise or fall?

5) Thyroid gland
    Thyrotropin RH > AP > thyrotropin (TSH) > thyroid > T3 & T4 > body metabolism
    T3 & thyroxine (T4) are also vital for nervous system development in infants
    The symptoms of hypothyroidism; & hyperthyroidism fig 9.
    Goiter, is due to over secretion of TSH, happens if thyroid H secretion is LOW.
    Calcitonin is also secreted by the thyroid gland (but see next gland for discussion)

CHECKPOINT not in textbook
The test to determine if your thyroid gland is normal is to measure TSH
If TSH is high are you hypothyroid or hyperthyroid?
If you take a thyroid prescription should the dose be higher or lower in the winter?

NEXT TWO: parathyroid & pancreas secretions are set by the plasma level of chemicals

6) Parathyroid secretes parathyroid H (PTH), regulates blood calcium level, fig 10
    calcium homeostasis, BUT calcitonin is not important for calcium homeostasis!
    PTH raises blood calcium: causes bones to release calcium into plasma,
    BUT PTH also decreases calcium excretion, & increases calcium absorption in guts, via vitamin D,
    so PTH increases calcium in body.  Hypocalcemia,  Rickets: too little vitamin D

7) Endocrine pancreas, ~2%, fig 11, secretes insulin & glucagon (exocrine pancreas ~98%)
    the secretion of both H regulates blood sugar & is determined by blood sugar level
    insulin: lowers blood sugar by causing cells to absorb it, &
    glucagon: raises blood sugar by causing cells that store it (liver, skeletal muscle) to release it
    There are other mechanisms to raise blood sugar: stress H below, growth H
    Diabetes mellitus: Type I, no insulin, treat with insulin
                              Type II: cells are insenstive to insulin, treat: diet, exercise, & drugs
Diabetes mellitus is serious because insulin acts alone in lowering blood sugar!

Next, adrenals, & last, gonads, are controlled from the hypothalamus (except aldosterone)
8) Adrenal glands lie on top of kidneys, fig 12, adrenals are essential for handling stress: 
    Brief stress: inner adrenal medulla secretes epinephrine (EPI) for fight & flight
    fig 12: stress causes brain centers to activate sympathetic = RED nervous system including adrenal medulla
    > EPI raises: blood sugar, BP, cardiac output, breathing, metabolism, alertness

    Chronic stress: outer adrenal cortex secretes cortisol to survive: wiki, fig 12, stress
    hypothalamus: Corticotropin RH > AP > ACTH > adrenal cortex > cortisol > survive chronic stress
    cortisol has effects on metabolism which raise blood sugar & amino acids for use in healing
    Glucocorticoid drugs, = cortisol in high dose, are anti-inflammatory, BUT:  too much/too long

    Salt: adrenal cortex also secretes mineralocorticoid, aldosterone: (Table 1, p 548)
    conserves salt (NaCl) & H2O in kidneys > raises BP
    Aldosterone keeps the ratio of sodium to potassium normal in the internal environment,
    its secretion rises if the ratio of Na to K falls

4. Not in textbook:
   
5. Sex: adrenal cortex secretes weak androgen: important in females, even after menopuase
   

9) Gonad sex hormones: a) estrogens: female, b) progestins: female pregnancy, c) androgens: male
    control of secretion is above: hypothalamus > GnRH > AP > Gonadotropins > gonads > sex H

CHECKPOINT p 556 (diabetes & diuresis have similar meaning)
1. How is the close relationship between the nervous & endocrine systems illustrated by the hypothalamus & the pituitary?
2. Why does alcohol cause diuresis?    Why does glucose cause diuresis in a diabetic?
3. Why are calcitonin & parathyroid H described as antagonistic?   Insulin & glucagon?
4. Why does a large meal in an untreated diabetic cause blood sugar level to go off the charts?
5. Diabetes mellitus is due to high blood sugar, what is diabetes insipidus due to?
6. Short term stress is handled by ? adrenal H, & long term stress by ? adrenal H?
Not in 2e:
6. Some parents have treated their normal children with growth H, why?  What side effects? 
    6a. is GH anti-aging?
7. Mice: Regular feeding & no exercise have normal blood sugar,
             Fasting or exercise causes low blood sugar.  What could be wrong?

Evolution Connection: The Changing Roles of Hormones
  The diverse roles of prolactin (PRL) in vertebrates provide evidence that
   hormonal regulation was an early adaptation that changed over evolutionary time:
  in fish that migrate between salt & fresh water PRL helps regulate salt and water balance
  in amphibians it stimulates movement towards water & affects metamorphosis
  in reptiles?
  in birds PRL regulates fat metabolism & reproduction.
  amphibian metamorphosis is due to thyroxine. .estrogen is ancient.