Podcast
Questions and Answers
What are the two main hormones secreted by the posterior pituitary?
What are the two main hormones secreted by the posterior pituitary?
Oxytocin and ADH (antidiuretic hormone)
Which of the following is NOT a function regulated by the neuroendocrine system?
Which of the following is NOT a function regulated by the neuroendocrine system?
Growth hormone (GH) is regulated by a positive feedback loop.
Growth hormone (GH) is regulated by a positive feedback loop.
False
The ______ is a hormone that stimulates the release of thyroid hormone.
The ______ is a hormone that stimulates the release of thyroid hormone.
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What is the name of the portal system that connects the hypothalamus and the anterior pituitary?
What is the name of the portal system that connects the hypothalamus and the anterior pituitary?
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What is the main function of growth hormone?
What is the main function of growth hormone?
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Which of the following is a common theme of endocrine axes?
Which of the following is a common theme of endocrine axes?
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GH and prolactin are regulated the same way as other pituitary hormones.
GH and prolactin are regulated the same way as other pituitary hormones.
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What are the two main uses of GH antagonists?
What are the two main uses of GH antagonists?
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Which two hormones are primarily involved in stimulating ovulation?
Which two hormones are primarily involved in stimulating ovulation?
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What does LH primarily stimulate in males?
What does LH primarily stimulate in males?
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Prolactin has a preparation available to treat prolactin deficiency.
Prolactin has a preparation available to treat prolactin deficiency.
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What is the primary mechanism by which dopamine agonists affect prolactin production?
What is the primary mechanism by which dopamine agonists affect prolactin production?
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ACTH is a synthetic derivative of a naturally occurring hormone.
ACTH is a synthetic derivative of a naturally occurring hormone.
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What is the primary function of ACTH?
What is the primary function of ACTH?
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What is the primary use of desmopressin?
What is the primary use of desmopressin?
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What are the two primary effects of vasopressin antagonists?
What are the two primary effects of vasopressin antagonists?
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Vasopressin antagonists can be used for extended periods of time.
Vasopressin antagonists can be used for extended periods of time.
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Study Notes
Hypothalamic and Pituitary Agents
- The hypothalamus and pituitary gland work together in a neuroendocrine system to regulate many bodily functions, including growth, metabolism, and reproduction.
- The hypothalamus produces releasing hormones that trigger the release of tropic hormones from the anterior pituitary.
- These tropic hormones then stimulate hormone release from target glands.
- The anterior pituitary communicates with the hypothalamus via the portal venous system.
- The posterior pituitary stores and releases hormones produced in the hypothalamus, regulated by neural activation.
- These hormones include oxytocin and ADH (antidiuretic hormone).
- Endocrine axes are a common theme with releasing hormones from the hypothalamus regulating the release of anterior pituitary hormones that act on target glands to stimulate hormone release from the target gland.
- Negative feedback control mechanisms, where the end product inhibits the release of releasing and stimulating hormones, are key components of the system.
- Exceptions exist, such as GH and prolactin, where the hypothalamus regulates these hormones differently.
- Most hypothalamic/pituitary hormones are accessible, but a small fraction is used for clinical purposes, mostly for diagnostic use or hormone replacement in deficiencies.
Neuroendocrine System
- Regulates many functions like growth, metabolism, and reproduction.
- Growth, metabolism, reproduction.
Releasing Hormones from Hypothalamus
- Trigger tropic hormone release from anterior pituitary.
- Cause target gland hormones to be released from target glands.
- TRH releases TSH, which releases thyroid hormone.
- There are exceptions, like GH and prolactin, which are controlled differently.
- The hypothalamus and anterior pituitary communicate through a portal system.
Posterior Pituitary Hormones
- Produced in the hypothalamus, stored in the posterior pituitary.
- Release is regulated by neural activation of hypothalamic neurons.
- Include oxytocin and ADH (antidiuretic hormone).
GH Actions
- Works through Jak/Stat system.
- Effects primarily involve growth and metabolism.
- Stimulates bone lengthening, muscle growth, and fat breakdown.
- Mediates growth effects mainly through IGF-1.
GH Actions (cont.)
- Mixed effects on carbohydrate metabolism, with GH having opposite effects to insulin sensitivity.
- Reduces insulin sensitivity, leading to mild hyperinsulinemia and elevated blood glucose.
- IGF-1 has insulin-like effects on glucose transport.
Hypothalamic and Anterior Pituitary Tropic Hormones
- Hypothalamic tropic hormones include PRH, PIH, TRH, CRH, GHRH, GHIH, GnRH.
- Anterior pituitary tropic hormones include Prolactin, TSH, ACTH, GH, LH, FSH.
- These hormones target different areas in the body to produce various downstream effects.
Approved Uses of Growth Hormone
- Growth failure in children, due to factors like: GH deficiency, Noonan syndrome, Prader-Willi syndrome, Turner syndrome, idiopathic short stature.
- Improved metabolic state and body composition in adults, like GH deficiency, wasting in HIV patients, and short bowel syndrome.
Adverse Effects
- Pancreatitis, gynecomastia, intracranial hypertension, muscle aches, scoliosis, edema.
- Contraindicated for use in active malignancies.
GH Antagonists
- Used to treat GH-secreting tumors (acromegaly, gigantism, carcinoid tumors).
- Somatostatin analogs like octreotide have longer durations of action.
- Dopamine agonists like Bromocriptine and Cabergoline are effective.
- GH receptor blockers, like Pegvisomant, are used for acromegaly.
GnRH and Analogs
- Act through GPCRs on gonadotrophs in the pituitary.
- Pulsatile secretion is required for normal FSH and LH release.
- Sustained administration inhibits FSH and LH release.
- Used in prostate cancer treatment and women needing ovarian suppression.
- Includes leuprolide, goserelin, and others.
Leuprolide (Lupron Depot) and GnRH Analogs
- Given intravenously, intramuscularly, or intranasally, with a 3-hour half-life.
- Adverse effects may include hot flashes, headaches, sweats, depression, diminished libido, and breast atrophy.
- Contraindicated in pregnancy and breastfeeding.
- GnRH antagonists, like Ganirelix and Cetrorelix, are used in IVF.
- Elagolix is indicated for endometriosis.
Gonadotropins (FSH, LH, and hCG)
- FSH stimulates oocyte maturation and estrogen production.
- LH affects androgen synthesis and sperm production.
- hCG maintains the corpus luteum and stimulates testosterone production.
- Used for stimulating sperm production, inducing follicle development, and ovulation in females, especially fertility treatments (IVF).
- Recombinant forms like follitropin alfa and beta are available, as well as those extracted from urine in postmenopausal women.
Prolactin
- No prolactin preparations are used in prolactin deficiency.
- Dopamine agonists, like Bromocriptine and Cabergoline, are used for hyperprolactinemia and prolactinomas.
- These agonists are effective in reducing prolactin secretion.
ACTH (Adrenocorticotropic Hormone)
- A 39-amino acid peptide hormone.
- Synthetic derivative (ACTH1-24) is called Cosyntropin.
- Works through GPCRs (g-protein coupled receptors) to stimulate adrenal cortical hormone production and activity.
- Used to differentiate primary from secondary adrenal insufficiency.
Vasopressin (ADH) and Oxytocin
- ADH/oxytocin are peptide hormones with similar sequences stimulating uterine contractions and breast tissue myoepithelial contraction.
- ADH increases water permeability in the kidneys, lowering urine output.
- Oxytocin is involved in labor and milk ejection.
- Used to induce labor or reduce postpartum bleeding..
- Acts via GPCRs on the phosphoinositide system.
Oxytocin Receptor Antagonist
- Atosiban is an oxytocin receptor antagonist used in preterm labor.
- Not widely approved in many regions.
Vasopressin and Desmopressin
- Vasopressin (ADH) is a peptide hormone that increases water permeability, and is used for diabetes insipidus.
- Desmopressin is a synthetic analog used for the same indications, as well as for bleeding disorders.
- High-dose vasopressin can be used in pulseless arrest.
- Adverse effects may include headache, nausea, vomiting, abdominal cramping and hyponatremia and seizures.
Vasopressin Antagonists
- Conivaptan and Tolvaptan are selective V1/V2 and V2 receptor antagonists, respectively, primarily to treat hyponatremia.
- These drugs increase urinary free water clearance.
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Description
Test your knowledge on the endocrine system and hormones with this engaging quiz. Explore key functions, hormone interactions, and regulatory mechanisms that govern the neuroendocrine system. Perfect for biology students and enthusiasts alike!
