The Endocrine System & Hypothalamic Pituitary Axes

Question 1

How doe the endocrine system operate?

Answer 1

It operates on a system of inputs and outputs, with each being caused by either an internal or external cue.

Question 2

What are feedback loops?

Answer 2

An internal or external cue causes the endocrine system to operate on a system of inputs and outputs. They’re called feedback loops because the end result feeds back to either stimulate an action or inhibit an action.

Question 3

What do positive feedback loops do?

Answer 3

Stimulate actions

Question 4

What do negative feedback loops do?

Answer 4

Inhibit an action

Question 5

What do feedback loops help facilitate?

Answer 5

Homeostasis, which is internal balance and equilibrium to the body and its systems.

Question 6

What is the HP Axis?

Answer 6

The hypothalamic-pituitary axis.
Feedback loops occur multiple times a day with nearly every single hormone, and this communication between the brain and the endocrine glands is called the HPA.

Question 7

What does the HPA affect?

Answer 7

The functions of the thyroid gland, adrenal glands and gonads, as well as influencing human growth and development, lactation, mineral balance and blood pressure.

Hypothalamic-pituitary axis

Question 8

What triggers the negative feedback loop response?

Answer 8

When the hypothalamus produces a neurohormone, it stimulates the pituitary to send specific tropic hormones to target tissues, such as the adrenals, thyroid and gonads, which in turn produce their own hormones that trigger this loop.

Question 9

What is the HPA Axis?

Answer 9

The Hypothalamic-Pituitary-Adrenal Axis. It’s axis that most people are familiar with, as its primary role is to manage the body’s stress response by regulating cortisol and adrenaline output.

Question 10

What is the normal function of the HPA axis?

Hypothalamic-Pituitary-Adrenal Axis

Answer 10

When there is stress, the HPA axis responds by producing CRH & ACTH, which stimulates the adrenals to produce cortisol and adrenaline, intiating the fight or flight response.

When a certain blood concentration of cortisol & adrenaline is reached, it exerts the negative feedback loop and systemic homeostasis returns.

Question 11

What symptoms can result from HPA dysregulation and adrenal insufficiency?

Answer 11

• Decreased stress resiliency
• Extreme fatigue
• Brain fog
• Sleep disturbances such as insomnia and difficulty waking
• Dizziness upon standing
• mid-section weight gain
• decreased immunity
• low libido
• depression

Question 12

Repeated stressors can do what to H-P sensitivity to cortisol?

Answer 12

It can decrease the sensitivity, inhibiting the negative feedback, which will wind up increasing the production of CRH and ACTH and increasing Cortisol and adrenaline output as well.

Question 13

What does Cortisol do for the body?

Answer 13

It is the body’s primary “stress hormone” but it also is naturally anti-inflammatory in moderate amounts, helps to balance inflammation during times of stress, illness or infection, and regulates blood sugar levels, contributes to the body’s electrolyte balance, facilitates the body’s wake and sleep cycle, and plays a role in the immune system.

Question 14

What is the cortisol diurnal rhythm?

Answer 14

Cortisol fluctuates on a daily basis. Research also shows that cortisol can fluctuate on a monthly pattern independent of its diurnal rhythm.

Question 15

Should or shouldn’t cortisol and melatonin ideally be opposite each other?

Answer 15

They should be.

Question 16

When should cortisol be at its lowest levels?

Answer 16

During the first few hours of sleep.

Question 17

When does cortisol peak and what is the Cortisol Awakening Response?

Answer 17

It rises slowly in the early morning and peaks between 50-150% within the first 30 minutes of waking.

This is the CAR.

Question 18

What does excess cortisol do?

Answer 18

AKA cortisol dysfunction can impact sleep quality and impair the CAR by suppressing melatonin levels and interfering with quality REM sleep.

This is one reason why those with cortisol issues often experience grogginess or heightened symptoms first thing in the morning.

Question 19

What symptoms are typically the result of CAR hypofunction or hyperfunction?

Answer 19

• Mdinight waking and insomnia
• waking up feeling very alert, anxious or not being able to go back to sleep
• grogginess or heightened symptoms first thing in the morning

Question 20

What is the HPT Axis?

Answer 20

• The Hypothalamic-Pituitary-Thyroid Axis
• It’s function is to facilitate energy metabolism, thermogenesis, growth and development.

Question 21

What does the thryoid hormone do?

Answer 21

It’s necessary for every single cellular process and metabolis function in the body.

Question 22

What is Thyrotropin-Releasing Hormone (TRH)?

Answer 22

When energy is needed for the body to perform a specific action, it puts a request out for thyroid hormone, which the hypothalamus then receives and responds by producing TRH, which tells the pituitary to release thyroid-stimulating hormone (TSH).

The thyroid then pumps out T4 which then goes to the liver for conversion to T3. From there, T3 is delivered to the target tissues for energy production.

Question 23

What is T4?

Answer 23

The inactive form of thyroid hormone

Question 24

When is T4 converted to reverse T3?

Answer 24

During times when energy is needed to be conserved. This is said to turn off the T3-energy-producing engine with its biologically inactive state.

Question 25

What is hypothyroidism?

Answer 25

Where the thyroid doesn't respond properly to the TSH signal, producing less thryoid hormone than what's needed. In this case, we consider this dysfunction "glandular hypothyroidism" or "primary hypothyroidism" It is also commonly associated with the autoimmune conditions Hashimotos Thyroiditis.

Question 26

Where do the majority of thyroid issues stem from?

Answer 26

Areas outside of the thyroid. Could be nurtient deficiencies (specifically with iodine and/or the amino acid tyrosine), an elevation of dysfunction of thryoid-binding globulin, and/or cellular inflammation.

Question 27

What can cellular inflammation and increased oxidative stress result in?

Answer 27

Cellular hypothroidism.

Question 28

When does cellular hypothyroidism happen?

Answer 28

This can happen when the peripheral cells of the body convert the thryoid hormone into Reverse T3 due to elevated levels of inflammation, as a safety mechanism to conserve energy and reduce the number of free radicals and oxidative damage that is produced from too much metabolic actiivity. This is why it's important to ensure that Reverse T3 is included in thyroid panels.

Question 29

What is subclinical hypothyroidism?

Answer 29

When people experience symptoms of hypothyridism while demonstrating "normal" thyroid labs. This is why functional testing for the thyroid is so important because standard labs only show a small picture of what's really going on.

Question 30

What is the HPG Axis?

Answer 30

The Hypothalamic-Pituitary-Gonadal Axis

Question 31

What is the function of the HPG Axis?

Answer 31

To facilitate ovulation and steroid sex hormone production, such as the production of testosterone, estrogen, and progesterone.

Question 32

At what rate is GnRH pulsed during the follicular phase?

Answer 32

At a slow rate (<1 pulse per 2-3 hours) which triggers the pituitary to produce Follicle Stimulating Hormone.

Question 33

What does FSH do?

Answer 33

It travels to the ovaries and stimulates the ovarian follicles to grow and produce estrogen. Typically, as FSH rises, estrogen levels wll rise as well. As estrogen elevates, it has a suppressive response on FSH.

Question 34

What is GnRH?

Answer 34

* Gonadotropin hormone-releasing hormone. * The pituitary gland in your endocrine system uses gonadotropin-releasing hormone (GnRH) to stimulate the production of follicle-stimulating hormone and luteinizing hormone. These gonadotropins (hormones) make the sex hormones testosterone, estrogen and progesterone. GnRH is vital to your sexual maturity, sex drive and fertility.

Question 35

What happens when there is a sharp drop in the levels of estrogen?

Answer 35

This sends a negative feedback to the hypothalamus, telling it to increase its pulsation rate & frequency (>1 pulse per hour), which stimulates the pituitary to produce a higher concentration of Luteinizing Hormone. LH then plays a mjor role in facilitating ovulation, which is a necessary process for producing the hormone Progesterone.

Question 36

When does dysfunction typically occur in the HPG Axis?

Answer 36

Usually due to a disruption in GnRH, which can occur due to elevated stress, inflammation, and nutrient deficiencies as well as high levels of Prolactin and Androgens. When this happens, it can lower FSH levels, which can lead to lowered estrogen levels, inhibiting the LH surge, leading to anovulation and progesterone deficiency. Can manifest in cases such as PCOS and hypothalamic amenorrhea.

Question 37

What is the HPATG Axis?

Answer 37

The hypothalamic-pituitary-adrenal-thyroid-gonadal axis

Question 38

Is thyroid hormone needed in every metabolic process in the body?

Answer 38

Yes, meaning that the HPT axis has an influence on the HPA & HPG axes and if there is thyroid dysfunction, that can lead to dysnfunction down the line as well.

Question 39

Can corticosteroid production from the adrenals both positively and negatively affect the HPG axis and ovulatory function?

Answer 39

Yes, specificaly with the production of cortisol and androgens

Question 40

What happens when there is too much cortisol?

Answer 40

It can directly inhibit GnRH, FSH, LH, interfering with ovulatory health and function. In turn this can have a negative output on estrogen and progesterone production.