Anterior Pituitary Hormones: Analogues and Their Inhibitors

• Anterior Pituitary Hormones: Analogues and Their Inhibitors include GnRH analogues and dopamine agonists.
• Anterior Pituitary Hormones: Analogues and Their Inhibitors regulate growth, reproduction, and metabolism.

Physiology of the Anterior Pituitary

• The anterior pituitary secretes several key hormones regulated by hypothalamic-releasing and inhibiting factors.

Hormones Produced:

• Growth Hormone (GH)
• Prolactin
• Thyroid-Stimulating Hormone (TSH)
• Adrenocorticotropic Hormone (ACTH)
• Luteinizing Hormone (LH)
• Follicle-Stimulating Hormone (FSH)

Regulation:

• Stimulation: Releasing factors such as GHRH stimulate GH secretion.
• Inhibition: Inhibitory factors like somatostatin suppress GH release.

Key Anterior Pituitary Hormones

1. Growth Hormone (GH) and Its Analogues

• Somatropin (Recombinant GH):
  • Uses: GH deficiency (children/adults), Turner syndrome, chronic kidney disease.
  • Adverse Effects: Edema, arthralgia, hyperglycemia.
• Mecasermin (Recombinant IGF-1):
  • Uses: GH insensitivity in children.
  • Adverse Effects: Hypoglycemia (monitor glucose).

2. GH Inhibitors (Somatostatin Analogues):

• Octreotide, Lanreotide:
  • Mechanism: Mimic somatostatin to inhibit GH, TSH, glucagon, and insulin.
  • Uses: Acromegaly, secretory diarrhea (e.g., VIPomas), variceal bleeding.
  • Adverse Effects: GI disturbances, gallstones, bradycardia.

3.  Prolactin and Its Inhibitors

• Dopamine Agonists (Bromocriptine, Cabergoline):
  • Mechanism: Suppress prolactin secretion.
  • Uses: Hyperprolactinemia (galactorrhea, infertility), prolactin-secreting adenomas, Parkinson’s disease.
  • Adverse Effects: Nausea, headache, orthostatic hypotension, psychiatric disturbances.

 4. Other Anterior Pituitary Hormones

• Adrenocorticotropic Hormone (ACTH):
  • Analogues: Synthetic ACTH (cosyntropin) for adrenal insufficiency testing.
  • Inhibitors: Indirectly inhibited by glucocorticoids via negative feedback.
• Thyroid-Stimulating Hormone (TSH):
  • Analogues/Inhibitors: Direct pharmacological agents are less common; instead, thyroid hormone analogues or antithyroid drugs indirectly influence TSH levels via feedback.
• Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH):
  • Analogues: GnRH analogues (e.g., leuprolide) for prostate cancer, fertility treatments.
  • Inhibitors: GnRH antagonists (e.g., degarelix) suppress LH and FSH quickly.

Clinical Applications

• Acromegaly: Managed with GH inhibitors like octreotide.
• Prolactinomas: Treated with dopamine agonists.
• Diagnostic Testing: ACTH analogues used to assess adrenal function.
• Reproductive Disorders: GnRH analogues and antagonists used in fertility treatments and hormone-sensitive cancers.

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