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Flashcards in Principles of Endocrinology Deck (36)
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Why are petide hormones injected?

Digested if ingested


Which hormone type is being described below?

  • Synthesized as prehormones
  • Stored in membrane-bound secretory vescicles
  • Regulated at the level of secretion and synthesis
  • Often circulate in blood unbound
  • Usually administered by injection
  • Signal through transmembrane receptors


NOTE: Stimulus for their release probably comes from another hormone/ substrate/ mineral and they are released by exoxcytosis because they are in vesicles.


Which hormones use the cAMP secondary messanger?

  • Epinephrine and norepinephrine
  • Glucagon
  • Luteinizing hormone
  • Follicle stimulating hormone
  • Thyroid-stimulating hormone
  • Calcitonin
  • Parathyroid hormone
  • Antidiuretic hormone


Which hormones use the protein kinase secondary messanger?

  • Insulin,
  • Growth hormone
  • Prolactin
  • Oxytocin
  • Erythropoietin
  • Several growth factors

NOTE: GH and prolactin don’t use an auto tyrosine kinase method. They must be activated


Which hormones use calcium and/or phosphoinositides as a second messenger?

  • Epinephrine and norepinephrine
  • Angiotensin II
  • Antidiuretic hormone
  • Gonadotropin-releasing hormone
  • Thyroid-releasing hormone.


Which hormones use the cGMP second messenger?

  • Atrial naturetic hormone
  • Nitric oxide


List steroid hormones and the site of synthesis.

  • Cortisol
    • Adrenal cortex
  • Aldosterone
    • Adrenal cortex
  • Androgens
    • Adrenal cortex
  • Testosterone
    • Testes
  • Estrogens, Progesterone
    • Ovaries
    • Corpus Luteum
    • Placenta
  • 1,25-Dihydroxycholecalciferol
    • Kidneys



Precursor for steroid hormones



Process by which progesterone and cortisol are synthesized

1. LDL is endocytosed into the cytoplasm as a cholesterol ester

2. Cholesterol esters then join with acetyl CoA to form cholesterol

3. Cholesterol enters the mitochondria

4. Cholesterol is converted to pregnenolone via the side chain cleavage enzyme

5.Pregnenolone then enters the SER where it is converted to progesterone

6. Progeseterone is then convereted to 17-OH- Progesterone

7. 17-OH-Progesterone is then converted to 11- Deoxycortisol

8. 11-Deoxycortisol is converted to cortisol


Which hormone type is being described below?

  • Derived from enzymatic modification of cholesterol
  • Cannot be stored in secretory vesicles becuase of lipophilic nature
  • Regulated at the level of the enzymatic pathway required for their synthesis
  • Transported in the blood bound to transport proteins
  • Signal through intracellular receptors
  • Can be administered orally



Steroid hormones have sections of DNA called ______________.

Hormone response elements

NOTE: When they bind to regions of DNA they will stimulate or repress transcription of a particular gene


List amine hormones and their site of synthesis.

  • Dopamine
    • Hypothalamus
  • T3, T4
    • Thyroid
  • NE, EPI
    • Adrenal medulla
  • Melatonin
    • Pineal gland

NOTE: All of the above are made from tyrosine, with the exception of melatonin, which is made from tryptophan


Mechanism of synthesis of norepinephine/epinephrine.

1. Tyrosine is converted to L-Dopa via tyrosine hydroxylase

2. L-Dopa is convered to dopamine bia dopa decarboxylase

3. Dopamine is converted to norepinephrine via dopamine B- hydroxylase

4. Norepinephrine is converted to epinephrine via phenylethanolamine N- methyltransferase

NOTE: Norepinephrine is primarily found in nerve terminals of sympathetic systemEpinephrine is primary found in the adrenal medulla


Which hormone stimulates phenylethanolamine-N-methyltransferase?


Which hormone type is being described below?

  • Derived from the iodination of thyronines
  • Lipophilic, but stored in thyroid follicle by covalent attachment to thyroglobulin
  • Regulated at the level of synthesis, iodination, and secretion
  • Transported in blood tightly bound to proteins
  • Signal through intracellular receptors
  • Can be administered orally

Thyroid hormones


Which hormone type is being described below?

  • Derived from enzymatic modification of tyrosine
  • Stored in membrane-bound secretory vesicles
  • Regulated at the levl of secretion and through the regulation of the enzymatic pathway required for their synthesis
  • Transported in blood free or only loosely associated with proteins
  • ​Hydrophilic and signal through transmembrane G-protein-coupled receptors called adrenergic receptors.



IGF1 is made by the liver, under the control of _______.

Growth hormone

NOTE:  This the only growth factor that is considered a hormone.


_______________ opposes the proliferative effects of estradiol on the endometrium and down-regulates the estrogen receptor.



How do hormones upregulate hormone receptors?

  • Hormones increase the number or affinity of its receptors by increasing the synthesis of new receptors, decreasing degradation of its receptors, or activating receptors


What are the stimulators and inhibitors of prolactin?

  • Stimulators
    • TRH
    • TSH
    • Estrogen
  • Inhibitors
    • Dopamine
    • TH

NOTE: Dopamine inhibits cAMP


Which hormones are transported by corticosteroid binding globulin (CBG, transcortin)?

Cortisol, aldosterone


Which hormones are transported by thyroxine binding globulin (TBG)?

Thyroxine (T4), triiodothyronine


Which hormones are transported by sex hormone-binding globulin (SHBG)?

Testosterone, estrogen


Which hormones are transported by albumin?

Most steroids, thyroxine, T3


Which hormones are transported by transthyretin (prealbumin)?

Thyroxine, some steroids


Neurons of which nucleus are responsible for circadian rhythm?

Suprachiasmatic nucleus

NOTE: Neurons of the suprachiasmatic nucleus impose a daily rhythm, called circadian rhythm, on the secretion of hypothalamic releasing hormones and the endocrine axes that they control as well as on other body functions.


Which hormonal axes are affected by aging?

  • Hypothalamic-pituitary-gonadal axis in women
  • GH-IGF system
  • The male hypothalamic-pituatary gonadal axis
  • Zona reticularis of adrenal cortex


What happens to LH, FSH, estrogen, and pregnanediol glucuronide (PDG) respectively as we age?

  • LH doesn't change much
  • FSH and estrogen levels increase
  • Pregnanediol glucuronide (PDG) levels are decreased


Which hormones decrease with aging?

  • Dehydroepiandrosterone (DHEA)
  • Pregnenolone
  • GH and IGF-1
  • Melatonin


Which hormones increase with aging?

  • FSH and Sex Steroid Binding Globulin (Men)
  • Gonadotropins (women)
  • PTH
  • Norepinephrine
  • Vasopressin
  • Atrial Natriuretic Peptide