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Molecular Endocrinology > Hormonal Axes > Flashcards

Hormonal Axes Flashcards

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1
Q

Name the two most important body´s hormonal axes.

A

-HPG axis: Hypothalamus, Pituitary, Gonades
- GH axis: Growth hormone

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2
Q

What are the three components of sex development ?

A
  • Chromosomal sex
  • Gonadal sex
  • Phenotypic sex
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3
Q

Describe in general the actions in the HPG axis.

A
  • Hypothalamus secrets GnRH
  • GnRH stimulates the anterior pituitary to secrete LH and FSH
  • These two hormones stimulate the gonades to secrete estrogen and progesterone in women and testosterone in men
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4
Q

How differs the regulation of the HPG axis in men and women ?

A
  1. Regulation in men:
    - Testosterone is produced in the testes
    - Testosterone downregulates the secretion of GnRH in the hypothalamus
    - Testosterone downregulates the secretion of LH and FSH in the anterior pituitary
  2. Regulation in women:
    - Estrogen and progesterone are produced in the ovaries
    - Both hormones regulate the secretion of GnRH in the hypothalamus and LH and FSH in the anterior pituitary in a feedback loop
    - Progesterone and estrogen can be up- or downregulating depending on the menstrual cycle
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5
Q

Name six hormones of the pituitary and their target organs.

A
  1. Prolactin: Mammary glands
  2. GH: Musculoskeletal system
  3. TSH: Thyroid gland
  4. ACTH: Adrenal cortex
  5. LH: Ovaries / Testes
  6. FSH: Ovaries / Testes
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6
Q

What is GnRH and how is it regulated ?

A
  • Gonadotropin-releasing hormone
  • GnRH is a hypothalamic neuropeptide
  • It is regulated by kisspeptin and neurokinin B
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7
Q

What is the main function of GnRH ?

A

GnRH stimulates the production of LH and FSH with a signal via G_q

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8
Q

How is FSH structured ?

A
  • FSH is a gluco-di-peptide
  • It is composed of an alpha- and a beta subunit
  • In each subunit are two carbohydrate attachment sites
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9
Q

How is the alpha-subunit of FSH structured ?

A
  • It contains 92 amino acids
  • It contains two glycosylation sites
  • The alpha-subunit is identical in FSH and LH
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10
Q

How is the beta-subunit of FSH structured ?

A
  • It contains 111 amino acids
  • It contains two glycosylation sites
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11
Q

How is LH structured ?

A
  • LH is a gluco-di-peptide
  • It is composed of an alpha- and a beta subunit
  • It contains three carbohydrate attachment sites
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12
Q

How is the alpha-subunit of LH structured ?

A
  • It contains 92 amino acids
  • It contains two glycosylation sites
  • The alpha-subunit is identical in LH and FSH
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13
Q

How is the beta-subunit of LH structured ?

A
  • It contains 121 amino acids
  • It contains one N-linked glycosylation site
  • It contains one ore two sialic acid residues
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14
Q

How many women are diagnosed with endometriosis ? (in %)

A

11 %

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15
Q

What is Endometriosis ?

A

Endometriosis is a chronic medical condition where endometrial tissues grows outside the uterus, causing pain, inflammation, and often fertility issues.

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16
Q

What are the symptoms of endometriosis ?

A
  • Pain
  • Dysmenorrhea
  • Heavy irregular bleeding
  • Bloating, nausea and vomiting
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17
Q

Name one main function of the LH receptor in females.

A
  • LH receptor is a G_s coupled receptor
  • It activates the secretion of androstenedione from theca interstitial cells
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18
Q

Name one main function of the FSH receptor in females.

A
  • FSH receptor is a G_s coupled receptor
  • It activates the secretion of estrogen from follicular granulosa cells
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19
Q

Name one main function of the LH receptor in males.

A
  • LH receptor is a G_s coupled receptor
  • It activates the secretion of testosterone from Leydig cells
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20
Q

In males, LH and FSH interact to…

A
  • stimulate the secretion of testosterone and inhibin in Leydig and Sertoli cells
  • to drive spermogenesis
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21
Q

Which hormones are produced in the ovaries ?

A
  • Progesterone
  • Androstenedione
  • Estrogens
  • Inhibin
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22
Q

Which hormones are produced in the testes ?

A
  • Andogens
  • Estradiol
  • Inhibin
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23
Q

Which hormones are produced in the placenta during pregnancy ?

A
  • Progesterone
  • Estrogens
  • Human chorionic gonadotropin
  • Human placental lactogen
  • Inhibin
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24
Q

Which hormones are produced in the uterus during pregnancy ?

A
  • Prolactin
  • Relaxin
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25
Name five steroids.
- Testosterone - DHT - Estrone - Estradiol - Progesterone
26
Name the main effects of testosterone.
- Development of male reproductive organs - Expression of male sex features like hair-pattern and low-pitched voice - Sperm production - Increase of muscle growth - Reduction of cholesterol levels
27
Name the main effects of estrogen.
- Expression of female sex features like breast development, body shape and hair- pattern - Regulation of bone structure, collagen production and lipid metabolism
28
Name the main effects of progesterone.
- Build-up of the endometrium - Preparation of mammary glands for milk production - Increase of basal temperature during pregnancy
29
Name the three phases of the menstual cycle and the corresponding average basal temperatures.
- Menses: ~36,4°C - Proliferative phase: ~ 36,4°C - Secretory phase: ~ 36,7°C
30
Name the three phases of the female ovarian cycle.
- Follicular phase (~days 1-13) - Ovaluation (~day 14) - Luteal phase (~days 15-28)
31
Name the three classes of sex steroids.
- Estrogens - Androgens - Gestagens
32
To which kind of receptors are sex steroids binding ?
Type-1 nuclear receptors
33
Which hormonal process determines the time of ovulation ?
- GnRH stimulates the secretion of LH and FSH in the anterior pituitary - The increased secretion of LG and FSH stimulates the ovulation
34
In which age is the menopause starting usually ?
In the age of 46-55 years
35
Which hormonal changes starts in the menopause ?
- Increased secretion of FSH and LH - Decreased secretion of estrone and estradiol
36
How does a oxytocin cycle initiate birth ?
- Oxytocin is secreted in the pituitary and carried in the bloodstream to the uterus - Oxytocin stimulates contractions, which leads to the baby pushing against the cervix - Nerve impulses from cervis transmitted to brain - Brain stimulates pituitary to secrete oxytocin
37
Describe the feedback loop regulation of lactation.
- The baby´s suckling stimulates nerves leading to the hypothalamus - Hypothalamus stimulates pituitary to release oxytocin and prolactin - Oxytocin stimulates the release of milk from the storage - Prolactin stimulates milk production
38
What is PCOS and what is its main reason ?
- Polycystic ovary syndrome - Increased androgen levels
39
What are the symptoms of PCOS ?
- Irregular, missing or heavy periods - Excess of body- and facial hair - Acne and patches of thick and darker skin - Reduced fertility
40
How is the level of LH changing in childhood, puberty, reproductive years and menopause ?
- Childhood: Low levels of LH - Puberty: LH levels increase slightly - Reproductive years: The basal level of LH is slightly higher than in puberty and has a monthly peak - Menopause: LH levels get stable again in a slightly higher level than the peaks in the reproductive years
41
How are the levels of HCG, progesterone and estrogen changing in the three trimesters of pregnancy ?
First trimester: - HCG rises fastly and has the highest level of the three hormones - Progesterone rises slowly and has a higher level than estrogen in the whole pregnancy - Estrogen levels stay stable and low Second trimester: - HCG levels decrease again - Progesterone levels stay stable - Estrogen levels increase slowly Third trimester: - HCG level is now the lowest and stay stable - Levels of progesterone and estrogen increase
42
What are the four components of sports performance ?
1. Skill - Speed - Reflexes - Coordination - Concentration 2. Strenght - Muscle mass 3. Stamina - Hemoglobin - Maximum oxygen transfer 4. Recovery - Tissue repair after injury and training
43
Name two types of hormones which can be used to dope the skill in sports performance.
- Ampetamine - Glucocorticoids (Both are Beta-blocker stimulants)
44
Name three hormones which can be used to dope the strenght in sports performance.
- Androgens - LH - Anti-estrogens
45
Name one hormone which can be used to dope the stamina in sports performance.
Erythropoietin
46
Name two hormones which can be used to dope the recovery in sports performance.
- Growth hormone (GH) - Growth hormone releasing hormone (GHRH)
47
Name the main function of inhibin in the HPG feedback loop.
Inhibition of FSH secretion
48
Name the main function of activin in the HPG feedback loop.
Stimulation of FSH secretion
49
Describe the HPG feedback loop of spermatogenesis.
- Secretion of GnRH in the hypothalamus - GnRH stimulates the secretion of LH and FSH in the anterior pituitary - LH stimulates the secretion of testosterone in the interstitial cells - Testosteron stimulates the spermatogenesis - FSH stimulates the production of androgen-binding protein (ABP) in sertoli-cells - ABP stimulates the spermatogenesis - FSH stimulates the secretion of inhibin in sertoli-cells - Inhibin inhibits the secretion of FSH and LH in the anterior pituitary
50
What are the symptoms of adult GH deficiency ?
- Increased body fat - Reduced muscle bulk - Reduced strength and physical fitness - Reduced sweating - Reduced concentration - Depression - Increased social isolation
51
Describe the feedback regulation in the GH axis.
- Stress signals initiate the secretion of GHRH in the hypothalamus - GHRH stimulates the secretion of PKA in the pituitary - PKA stimulates the synthesis and secretion of GH - GH activates JAKs/STATs in the liver - JAKs/STATs stimulate the production of IGF-1 - IGF-1 inhibits the synthesis of GH in the pituitary - IGF-1 stimulates the production of somatostatin in the hypothalamus - Somatostatin inhibits the production of GH in the pituitary
52
What is the function of ghrelin in the feedback regulation of the GH axis ?
- Ghrelin is released in the stomach during hunger - Ghrelin stimulates the production of GHRH in the hypothalamus, which leads to an increased GH production - Ghrelin stimulates the secretion of GHS-R in the pituitary which also leads to an increased GH production
53
How does the circadian rythm of GH secretion look like ?
- GH is produced in pulses (2-3 during awake time) - Increased GH production during sleep (more pulses with higher intensity)
54
Which two hormones belonging to the GH axis are produced in the hypothalamus ?
- Growth hormone-releasing hormone (GHRH) - Somatostatin (SST)
55
To which kind of receptor is GHRH binding ?
G-coupled receptor
56
What happens after GHRH binding to its receptor ?
- GH is released from storage - PKA is stimulated to phosphorylate CREB - CREB leads to the expression of Pit-1 - Pit-1 leads to the expression of the GH receptor - Pit-1 leads to the expression of GH
57
What is the general function of Somatostatin (SST)
Inhibition of multiple endocrine functions
58
What are the targets of SST ?
Somatropic cells in the pituitary and GHRH neurons
59
Explain how SST inhibits the depolarization of somatotrope cells.
- SST binds to G_i coupled receptors - Stimulation of Voltage-gated K+-channels leads to an increased export of K+ - Inhibition of voltage-gated Ca2+-channels leads to an decreased inport of Ca2+ - Hyperpolarisation of cell membrane
60
Name a special structural feature of GH and its reason.
- GH it occurs in two isoforms: GH1 and GH2 - They are created by alternative splicing at exon 3
61
Which kind of receptor is GHR ?
- Tyrosine-associated receptor - GHR is signaling via multiple pathways
62
IGF-1/2 has high similarities in sequence and signaling to which hormone ?
Insulin
63
What are the similarities and differences between insulin receptors and IGF-1 receptors ?
- They are similar structured in general (two extracellular α-subunits and two intracellular β-subunits) - Their α-subunits contain a cystein-rich domain - They differ in their binding domains
64
What is the reason for acromegaly ?
- GH excess in adultness - Can be caused by a tumor in the pituitary
65
How can acromegaly be treated ?
- Supply of SST ligands - Supply of GHR inhibitors

Molecular Endocrinology (2 decks)

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