Exam 4 | Endocrine pt. 2 Flashcards
What does the he Hypothalamic-Pituitary-Gonad (HPG) Axis do?
This pathway serves to regulate the production and release of the primary sex hormones in biological males (testosterone) and biological females (estrogen and progesterone), all of which are produced by the gonads.
Describe the step by step process of the hypothalamic-pituitary-gonad axis.
1) The hypothalamus regularly produces Gonadotropin Releasing Hormone (GnRH), which travels via the portal vein system to reach the anterior pituitary gland.
2) At the anterior pituitary gland, GnRH triggers the production and release of two hormones, Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH), which target the gonads in the periphery.
3) FSH and LH travel through the bloodstream to the gonads, where they then stimulate the production and release of testosterone (in biological males) and estrogen and (then) progesterone (in biological females).
4) Once a sufficient concentration (threshold) of these sex hormones have been produced and released in the periphery, they will participate in negative feedback (inhibition) of the production and release of FSH and LH (at the level of the anterior pituitary gland) and GnRH (at the level of the hypothalamus).
What does the Hypothalamo-Pituitary-Thyroid (HPT) Axis do?
It serves to regulate production and secretion of thyroid hormones (T3 and T4), which regulate various physiological processes including brain function, cardiovascular function, bone structure and metabolism.
Describe the step by step process for the Hypothalamo-Pituitary-Thyroid (HPT) Axis.
1) The hypothalamus regularly produces Thyroid Releasing Hormone (TRH), which travels via the portal vein system to reach the anterior pituitary gland.
2) At the anterior pituitary gland, TRH triggers the production and release of Thyroid Stimulating Hormone (TSH), which targets the thyroid gland.
3) TSH will travel through the bloodstream to the thyroid, where it will then stimulate the production and release of two peripheral thyroid hormones, Triiodothyronine (T3) and Thyroxine (T4).
4) Once a sufficient concentration (threshold) of these thyroid hormones have been produced and released in the periphery, they will participate in negative feedback (inhibition) of the production and release of TSH (at the level of the anterior pituitary gland) and TRH (at the level of the hypothalamus).
What does T3 and T4 do?
These hormones are produced from iodine derived from our diet (most commonly through the consumption of iodized salt), and regulate a variety of physiological processes including hair, skin and nail growth, weight and metabolism, mood and cognitive function, and much more.
What does FSH and LH do for biological males?
In biological males, FSH stimulates the production of sperm and generally remains at constant levels after puberty. LH stimulates the production of testosterone, and thus varies throughout a 24-hour cycle
What does FSH and LH do for biological females?
In biological females, FSH stimulates the production of eggs in the ovaries, and varies in concentration depending on the individual’s menstrual cycle.
LH stimulates the release of an egg from the ovaries during ovulation, and varies in concentration depending on the individual’s menstrual cycle.
What do parathyroid glands do?
These glands produce a hormone called parathyroid hormone (PTH) which works to regulate blood Calcium (Ca2+) levels throughout the circadian (24-hour) cycle; it maintains blood calcium homeostasis
What happens when blood calcium levels are high?
This triggers a decrease in the production of Parathyroid Hormone (PTH), which results in increased deposition of calcium onto the bone tissue (mediated by osteoblasts); make bones stronger
What happens when blood calcium levels are low?
The increase in bone deposition ultimately triggers a decrease in blood calcium levels, which in turn causes an increase in the production of PTH by the parathyroid glands. This activates the osteoclasts, which then break down bone tissue to restore calcium to the blood and increase blood calcium levels.
What does the Hypothalamo-Pituitary-Adrenal (HPA) Axis do?
It regulates the production and secretion of cortisol from the adrenal cortex, which plays an essential role in the body’s stress response.
Give a step by step process for the Hypothalamo-Pituitary-Adrenal (HPA) Axis.
1) Typically, environmental stressors will trigger the hypothalamus to produce and secrete Corticotropin Releasing Hormone (CRH), which travels via the portal vein system to reach the anterior pituitary gland.
2) At the anterior pituitary gland, CRH triggers the production and release of Adrenocorticotropic Hormone (ACTH), which targets the adrenal glands.
3) ACTH will travel through the bloodstream to the adrenal cortex, where it will then stimulate the production and release of cortisol, considered to be the quintessential “stress hormone”. Cortisol signals downstream to the immune system, with mixed results (in some ways, cortisol production can augment the function of the immune system, but excess cortisol production can lead to decreased immune function, hence why college students are more prone to coming down with a cold or flu at the height of final exam season).
4) Once a sufficient concentration (threshold) of cortisol has been produced and released in the periphery, it will signal via negative feedback (inhibition) back to the hypothalamus to reduce the production of CRH.
What happens in cases of chronic stress?
In cases of chronic stress, one’s tolerance for endogenous cortisol may increase, affecting this negative feedback loop by reducing the level of inhibition on the hypothalamus (becoming weaker), leading to tonically higher levels of cortisol. Cortisol levels can be measured via blood tests, as well as through saliva samples.
Who are more effected by thyroid diseases?
Conditions that affect the thyroid gland, biological females are much more prone to experiencing either hypothyroidism or hyperthyroidism, depending upon the balance of the sex hormones (estrogen, progesterone AND testosterone) circulating in the body at any given moment in time.
What is hypothyroidism?
Hypothyroid Disease (hypothyroidism) is characterized by an inability of the thyroid to produce sufficient levels of T3 and T4 to maintain metabolic homeostasis.
What are some symptoms of hypothyroidism?
Cold intolerance
Dry hair
Puffy face
Goiter
Slower heartbeat (bradycardia)
Weight gain
Constipation
Fertility problems/ infertility
Irregular menstrual cycle
How do you treat hypothyroidism?
The most common treatment for hypothyroidism is pharmacological in nature (oral medication of synthetic thyroid hormone supplements).
What is hyperthyroidism?
Hyperthyroid Disease (hyperthyroidism) is characterized by an overproduction of T3 and T4, leading to a myriad of metabolic and other issues.
What are symptoms for hyperthyroidism?
Heat intolerance
Hair loss
Bulging eyes
Goiter
Rapid heartbeat (tachycardia)
Weight loss
Diarrhea
Infrequent periods (menses)
How do you treat hyperthyroidism?
The most common treatments for hyperthyroidism include ingestion of radioactive iodine (a form of pharmacological radiation therapy), oral medications, and in severe cases, surgery.
What is goiter?
Goiter is a relatively rare condition (in developed conditions) that results from insufficient iodine consumption from one’s diet. Lack of iodine, which is a necessary chemical substrate for the production of thyroid hormones, results in swelling of the thyroid gland and over time, the development of nodules on the surface of the thyroid. Depending on the severity, this swelling may be dramatic and easily visible from outside the body.
How do you treat goiter?
It is not uncommon for patients with goiter to be prescribed radioactive iodine to both, supplement the lack of iodine as well as serve as a form of radiation therapy to destroy the nodules and reduce the swelling of the gland.
In more severe cases, surgery may be necessary to reduce swelling and restore normal thyroid function.
What roles does the liver serve?
The liver is one of the most essential accessory organs in the digestive system. It plays an important role in processing drugs and other toxic chemicals that enter the body, but it also is the site of storage of glucose in the form of glycogen (glucogenosis).
When is glycogen released from the liver?
When cells in the body (specifically skeletal muscle cells and neurons) require energy, the liver will break down glycogen to release glucose into the bloodstream
