hypothalamus and pituitary 2 Flashcards by Monica Palumbo

hypothalamic-pituitary-adrenal axis

hypothalamus secretes corticotropin-releasing hormone

stimulates adrenocorticotrophic hormone, melanocyte stimulating hormone and B-endorphin production at the anterior pituitary from proopiomelanocortin (POMC) precursor

stimulates adrenal glucocorticoid and androgen production at the adrenal cortex

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CRH stimulates

Stimulates ACTH, MSH, and β-endorphin secretion from proopiomelanocortin (POMC) precursor

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what causes CRH levels to decrease

CRH levels decrease after long-term steroid treatment via negative feedback.

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ACTH stimulates

Stimulates adrenal glucocorticoid and androgen production

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why do you get hyperpigmentation in Cushing’s disease

ACTH and MSH share the common precursor POMC, which explains the hyperpigmentation seen in Cushing disease.

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hypothalamic pituitary-thyroid axis

thyrotropin-releasing hormone from the hypothalamus stimulates TSH and prolactin secretion from the pituitary
TSH stimulates thyroid hormone production

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What does TRH stimulate?

TSH and prolactin secretion

TRH stands for Thyrotropin-Releasing Hormone.

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What condition may result from an increase in TRH levels?

Galactorrhea

This can occur due to stimulation of prolactin secretion by increased TRH levels in primary/secondary hypothyroidism.

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What is the role of TSH?

Stimulates thyroid hormone production

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What inhibits TSH secretion?

Dopamine, somatostatin, and glucocorticoids

These substances play a regulatory role in thyroid hormone production.

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What is the best initial test in the workup of hypothyroidism?

TSH levels

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What axis involves the relationship between the hypothalamus, pituitary gland, and gonads?

Hypothalamic-pituitary-gonadal axis

This axis is important for reproductive hormone regulation.

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What does GnRH stimulate?

FSH and LH secretion

GnRH stands for Gonadotropin-Releasing Hormone.

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What occurs during breastfeeding due to high prolactin levels?

Suppressed GnRH secretion, resulting in lactational amenorrhea, a physiological amenorrhea that causes a delay in the resumption of ovulation in women who breastfeed exclusively and lasts for about 10 months

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What is responsible for puberty and reproductive function?

Pulsatile GnRH secretion

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What triggers ovulation in female individuals?

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What stimulates testosterone synthesis in Leydig cells in male individuals?

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What does FSH stimulate?

The maturation of germ cells in both male and female individuals

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hypothalamic-pituitary-somatotrophic axis

growth hormone releasing hormone stimulates growth hormone secretion from the pituitary

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What does GHRH stand for?

Growth Hormone-Releasing Hormone

GHRH stimulates GH secretion.

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What is the primary function of GHRH?

Stimulates GH secretion

Synthetic forms of GHRH, such as tesamorelin, can be used for abdominal fat reduction in HIV-associated lipodystrophy.

What is GH commonly known as?

Growth hormone or somatotropin

List the direct effects of GH.

↓ Glucose uptake into cells (↑ insulin resistance)
↑ Lipolysis
↑ Protein synthesis in muscle
↑ Amino acid uptake

What are the indirect effects of GH mediated by?

IGF-1 (insulin-like growth factor 1)
growth stimulation/anabolic effect on the body

IGF-1 was originally called somatomedin C.

What factors increase GH secretion?

* Exercise * Deep sleep * Puberty * Hypoglycemia * Chronic kidney disease (CKD) * Thyroid hormone * Estrogen * Testosterone * Short-term glucocorticoid exposure ## Footnote These factors can stimulate the release of GH from the pituitary gland.

What factors decrease GH secretion?

* Glucose * Somatostatin * Somatomedin * Free fatty acids * Chronic glucocorticoid therapy ## Footnote These factors inhibit the secretion of GH.

What is the role of somatostatin?

Inhibits GH and TSH secretion ## Footnote Synthetic forms of somatostatin, such as octreotide, are used in the treatment of acromegaly.

Fill in the blank: Synthetic forms of GHRH can be used for _______.

abdominal fat reduction in HIV-associated lipodystrophy ## Footnote Tesamorelin is a synthetic form of GHRH.

Hypothalamic-pituitary-prolactin axis

TRH from the hypothalamus stimulates prolactin secretion at the anterior pituitary which acts directly on the mammary gland to promote lactation

What does dopamine inhibit in the hypothalamic-pituitary-prolactin axis?

Secretion of prolactin in the pituitary gland ## Footnote Dopamine is also known as prolactin-inhibiting hormone.

Which hormone has a higher influence on prolactin regulation?

Dopamine (inhibitory)

What is the primary function of prolactin secreted by lactotropic cells?

↑ Breast tissue growth and lactation

What effect does prolactin have on GnRH secretion?

Inhibits GnRH secretion

In female individuals, elevated prolactin levels can lead to _______.

Amenorrhea inhibition of ovulation galactorrhea decreased libido

What condition in females is characterized by the secretion of milk not associated with childbirth?

Galactorrhea

In male individuals, what is one consequence of increased prolactin levels?

Inhibition of spermatogenesis decreased libido

In both genders, what is a common effect of elevated prolactin levels?

Decreased libido

What hormone stimulates the secretion of prolactin?

TRH

What hormone regulates plasma osmolality?

Antidiuretic hormone (ADH) ## Footnote ADH is also known as vasopressin.

What senses plasma osmolality?

Hypothalamic osmoreceptors ## Footnote These receptors detect changes in the concentration of solutes in the blood.

What senses hypovolemia?

Atrial stretch receptors ## Footnote These receptors monitor the volume of blood returning to the heart.

What senses hypotension?

Peripheral baroreceptors ## Footnote These receptors are located in blood vessels and respond to changes in blood pressure.

What hormone is sensed by hypothalamic receptors in relation to blood pressure regulation?

Angiotensin II ## Footnote Angiotensin II plays a crucial role in blood pressure regulation.

What effect does ADH have on urea reabsorption?

Increases urea reabsorption in the collecting duct ## Footnote This enhances the corticomedullary gradient, aiding urine concentration.

What condition is characterized by elevated ADH despite plasma hypoosmolality?

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) ## Footnote SIADH leads to water retention and dilutional hyponatremia.

What condition can result from ADH deficiency or resistance?

Diabetes insipidus ## Footnote This condition leads to excessive urination and thirst.

What is a second-line therapy for septic shock?

ADH ## Footnote ADH helps increase organ perfusion in septic shock.

What effect does alcohol have on ADH?

Inhibits ADH release ## Footnote This inhibition leads to increased diuresis.

What physiological response is stimulated by nipple stimulation?

Oxytocin release ## Footnote Nipple stimulation triggers milk ejection during breastfeeding.

What stimulates oxytocin release during labor?

Stretching of the vagina or cervix ## Footnote This promotes uterine contractions.

What reflex does oxytocin facilitate?

Milk ejection reflex via myoepithelial cell contraction ## Footnote This reflex involves contraction of myoepithelial cells around mammary glands.

In addition to its role in reproduction, what behaviors is oxytocin involved in?

Social and reproductive behavior, fear, anxiety, and depression ## Footnote Oxytocin is often referred to as the 'love hormone' due to its effects on social bonding.