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Questions and Answers
Which hormone is primarily secreted by somatotropes?
Which hormone is primarily secreted by somatotropes?
What is a primary function of thyrotropes in the adenohypophysis?
What is a primary function of thyrotropes in the adenohypophysis?
What triggers the secretion of adrenocorticotropic hormone (ACTH) from the adenohypophysis?
What triggers the secretion of adrenocorticotropic hormone (ACTH) from the adenohypophysis?
Which of the following hormones is primarily associated with the regulation of gonadal functions?
Which of the following hormones is primarily associated with the regulation of gonadal functions?
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What primarily stimulates the release of anti-diuretic hormone (ADH)?
What primarily stimulates the release of anti-diuretic hormone (ADH)?
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What role does thyroid stimulating hormone (TSH) primarily serve in the body?
What role does thyroid stimulating hormone (TSH) primarily serve in the body?
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Which hormones are responsible for regulating the function of the gonads?
Which hormones are responsible for regulating the function of the gonads?
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What is the primary function of adrenocorticotropic hormone (ACTH)?
What is the primary function of adrenocorticotropic hormone (ACTH)?
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How does growth hormone (GH) primarily regulate metabolism?
How does growth hormone (GH) primarily regulate metabolism?
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What is the feedback mechanism of insulin-like growth factor-1 (IGF-1) on growth hormone (GH)?
What is the feedback mechanism of insulin-like growth factor-1 (IGF-1) on growth hormone (GH)?
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What is the significance of the diurnal pattern observed in the release of adrenocorticotropic hormone (ACTH)?
What is the significance of the diurnal pattern observed in the release of adrenocorticotropic hormone (ACTH)?
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Which of the following receptors are associated with hormone regulation in the adrenal cortex?
Which of the following receptors are associated with hormone regulation in the adrenal cortex?
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Which layer of the hypothalamus is involved in the release of hypophysiotropic hormones?
Which layer of the hypothalamus is involved in the release of hypophysiotropic hormones?
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What physiological action is stimulated by thyrotropin-releasing hormone (TRH)?
What physiological action is stimulated by thyrotropin-releasing hormone (TRH)?
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Which hormone is primarily responsible for stimulating the development of ovarian follicles in females?
Which hormone is primarily responsible for stimulating the development of ovarian follicles in females?
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Which condition is associated with abnormally low circulating levels of anti-diuretic hormone (ADH)?
Which condition is associated with abnormally low circulating levels of anti-diuretic hormone (ADH)?
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Which hormone stimulates the secretion of breast milk in lactating females?
Which hormone stimulates the secretion of breast milk in lactating females?
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What is a physiological effect of abnormally high levels of circulating ADH?
What is a physiological effect of abnormally high levels of circulating ADH?
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What primary action does gonadotropin-releasing hormone (GnRH) perform at the anterior pituitary?
What primary action does gonadotropin-releasing hormone (GnRH) perform at the anterior pituitary?
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How does thyroid-stimulating hormone (TSH) affect the thyroid gland?
How does thyroid-stimulating hormone (TSH) affect the thyroid gland?
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Which hormone regulates metabolic rate and is produced by the thyroid gland?
Which hormone regulates metabolic rate and is produced by the thyroid gland?
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What is the effect of low levels of growth hormone during development?
What is the effect of low levels of growth hormone during development?
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Which hormone is responsible for regulating spermatogenesis in males?
Which hormone is responsible for regulating spermatogenesis in males?
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What is the primary function of adrenocorticotropic hormone (ACTH)?
What is the primary function of adrenocorticotropic hormone (ACTH)?
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Which hormone stimulates ovulation and the formation of the corpus luteum in females?
Which hormone stimulates ovulation and the formation of the corpus luteum in females?
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Which hormone is released by somatotropes in the anterior pituitary?
Which hormone is released by somatotropes in the anterior pituitary?
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What effect does growth hormone (GH) have on the body?
What effect does growth hormone (GH) have on the body?
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Which hormone stimulates the production of testosterone in males?
Which hormone stimulates the production of testosterone in males?
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What role does corticotropin-releasing hormone (CRH) play in the endocrine system?
What role does corticotropin-releasing hormone (CRH) play in the endocrine system?
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Which hormone is primarily involved in the regulation of insulin-like growth factor?
Which hormone is primarily involved in the regulation of insulin-like growth factor?
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What is a key function of glucocorticoids produced by the adrenal cortex?
What is a key function of glucocorticoids produced by the adrenal cortex?
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Which hormone counters some actions of insulin?
Which hormone counters some actions of insulin?
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What primary role does IGF-1 play in the endocrine system?
What primary role does IGF-1 play in the endocrine system?
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Which hormone is responsible for stimulating breast milk production?
Which hormone is responsible for stimulating breast milk production?
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What is a characteristic symptom of gonadotropin-secreting adenomas?
What is a characteristic symptom of gonadotropin-secreting adenomas?
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Which hormone is NOT coordinated by the adenohypophysis?
Which hormone is NOT coordinated by the adenohypophysis?
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What type of feedback is primarily involved in the regulation of the HPA axis?
What type of feedback is primarily involved in the regulation of the HPA axis?
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Which hormone is secreted by the neurohypophysis?
Which hormone is secreted by the neurohypophysis?
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What can occur as a result of hypopituitarism?
What can occur as a result of hypopituitarism?
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Which of the following hormones is NOT released from the adenohypophysis?
Which of the following hormones is NOT released from the adenohypophysis?
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Gonadotropin-secreting adenomas typically result in low levels of which two hormones?
Gonadotropin-secreting adenomas typically result in low levels of which two hormones?
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Which structure is classified as true endocrine tissue?
Which structure is classified as true endocrine tissue?
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Study Notes
Hypothalamic-Pituitary Axis (HPA)
- The HPA is the most important part of the endocrine system
- It controls the thyroid, adrenal, and reproductive glands
- It regulates somatic growth, lactation, milk secretion, and water metabolism
Learning Outcomes
- Understand the structure and anatomy of the HPA
- Compare anterior and posterior pituitary regarding cell types, vascular supply, and hypothalamic innervation
- Identify the six key anterior pituitary hormones, their target tissues, and functions
- Identify and understand the functions of two key posterior pituitary hormones
- Understand how pituitary tumors affect pituitary function and physiology
Recommended Reading
- Endocrine and Reproductive Physiology, 4th Edition, Elsevier, Chapter 5 (pp. 99-129)
- Salhadar, K., et al. (2021). Phosphoproteomic identification of vasopressin/cAMP/protein kinase A-dependent signaling in kidney. Molecular Pharmacology, 99, 358-369. (https://doi.org/10.1124/mol.120.119602)
- Arrowsmith, S., and Wray, S. (2014). Oxytocin: Its mechanism of action and receptor signaling in the myometrium. Journal of Neuroendocrinology, 26, 356-369. (https://doi.org/10.1111/jne.12154)
- BS21002 - Cellular communication - Steroid hormones
- BS21002 - Cellular communication - Peptide hormones
Anatomy of the Pituitary Gland
- The pituitary gland has two parts: anterior and posterior
- The anterior pituitary is derived from oral ectoderm
- The posterior pituitary is derived from the forebrain
- The hypothalamus regulates hormone release by the pituitary gland.
Development of the Pituitary Gland
- Neurohypophysis: downgrowth of the forebrain
- Adenohypophysis: oral ectoderm of the roof of the stomatodeum
Cells of the Pituitary Gland
- Adenohypophysis: endocrine tissue with distinct cell types for hormone release:
- Somatotropes
- Corticotropes
- Thyrotropes
- Gonadotropes
- Lactotropes
- Neurohypophysis: neural tissue for transport and storage of hypothalamic hormones
Vascular Supply of the Pituitary Gland
- Hypothalamic neurons release hormones into the portal system
- Superior hypophyseal artery supplies the portal system, which branches into the secondary plexus
- Secondary plexus of the hypophyseal portal system supplies the adenohypophysis
Innervation of the Pituitary Gland
- Hypothalamohypophysial portal system transports hypothalamic hormones to the anterior pituitary.
- Posterior pituitary receives hormones directly from the hypothalamus via the hypothalamo-hypophyseal tract.
Neurohypophysis (Posterior Pituitary)
- Supraoptic nuclei = antidiuretic hormone (ADH)
- Paraventricular nuclei = oxytocin
Anti-diuretic Hormone (ADH) - Secretion
- Stimulated by: increased plasma osmolality, decrease in blood pressure, stress, and pain.
Anti-diuretic Hormone (ADH) - Physiological Effects
- ADH increases permeability of distal tubules and collecting ducts to water.
- This increases water reabsorption and blood volume
- ADH causes vasoconstriction and reduced cardiac output.
- Independent of solute movement
Anti-diuretic Hormone (ADH) - Disorders
- Abnormally high ADH: high urine osmolality, edema (high plasma volume)
- Abnormally low ADH: diabetes insipidus
Oxytocin
- Stimulates milk secretion in lactating females
- Contributes to parturition
Oxytocin - Secretion
- Stimulated by: suckling, vaginal/cervical stimulation, and crying
Oxytocin - Physiological Effects
- Initiates milk letdown (myoepithelial cell contraction)
- Increases milk production (prolactin)
Adenohypophysis (Anterior Pituitary)
- Hypothalamus releases hormones via the hypophyseal portal system and these hormones reach the anterior pituitary (adenohypophysis)
- Anterior pituitary is an endocrine gland that releases hormones directly into the bloodstream.
Adenohypophysis - Hypophysiotropic hormones
- Hormones that stimulate the release of other hormones from the anterior pituitary
Summary - Adenohypophysis Hormones
- Hypophysiotropic hormones (from hypothalamus) stimulate adenohypophysis hormones
- Adenohypophysis hormones (tropic hormones) stimulate other endocrine glands to produce more hormones
Adenohypophysis Hormones (thyroid stimulating hormone (TSH))
- Regulates thyroid function via TSH receptor on thyroid epithelial cells, and T3 and T4 support tropic effects on growth and metabolism
Adenohypophysis Hormones (Follicle stimulating hormone (FSH) and Luteinizing hormone (LH))
- Regulate the function of the gonads (ovaries and testes) in both males and females via their target receptors
Adenohypophysis Hormones (Adrenocorticotropic hormone (ACTH))
- Shows a diurnal pattern
- Stimulates adrenal cortex via MC2R receptor to increase cortisol and adrenal androgen production
- Cortisol inhibits ACTH secretion
Adenohypophysis Hormones (Growth hormone (GH))
- Regulates metabolism via GH receptor in the liver
- Results in the production of IGF-1 and negative feedback
- Negative feedback inhibits GH secretion
Adenohypophysis Hormones (Prolactin)
- Stimulates breast milk production via reduced dopamine release from parvicellular hypothalamic neurons
Feedback Loops in HPA Regulation
- Tropic hormones provide negative feedback to regulate hormone release
Gonadotropin-secreting Adenomas
- Rare pituitary tumors
- Secrete low FSH and LH
- Symptoms usually depend on tumor size (headaches, visual field defects)
Note on HPA
- The most dominant part of the endocrine system
- Pituitary (adenohypophysis & neurohypophysis) is embryologically different and has different structure and mechanisms
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Description
Explore the Hypothalamic-Pituitary Axis (HPA) and its crucial role in the endocrine system. This quiz covers the anatomy of the HPA, the functions of anterior and posterior pituitary hormones, and the impact of pituitary tumors on physiology. Test your knowledge and understanding based on the recommended reading from Endocrine and Reproductive Physiology.
