Endocrinology: Somatotropic Cells and Growth Hormones

Growth Hormone-Releasing Hormone (GHRH)

• GHRH stimulates the release of growth hormone (GH) from somatotrophs in the anterior pituitary gland.
• It plays a crucial role in regulating growth and metabolism through its action in the hypothalamic-pituitary axis.

Inhibition of Growth Hormone Release

• Somatostatin inhibits the release of growth hormone from somatotrophs, acting as a negative regulator.
• It is essential for maintaining hormonal balance in the body.

Hormones Affected by Somatostatin

• Somatostatin also inhibits the release of thyroid-stimulating hormone (TSH) and insulin.
• It functions as an inhibitory hormone impacting multiple endocrine pathways.

Regulation of Growth Hormone Secretion

• Growth hormone secretion is regulated by GHRH stimulation and somatostatin inhibition in somatotropic cells.
• This regulation ensures that GH levels respond appropriately to the body’s needs.

Stimulation of Growth Hormone Secretion

• Ghrelin, an appetite-stimulating hormone, also stimulates growth hormone secretion in normal individuals.
• It works in conjunction with GHRH for optimal GH release.

Role of Bromocriptine

• Bromocriptine acts as a dopamine agonist and can inhibit growth hormone release.
• It is used therapeutically to manage conditions involving excess GH.

Function of Gonadotrophins

• Gonadotrophins (LH and FSH) are critical in regulating reproductive hormones and processes.
• They stimulate gonadal function and influence sex hormone production in both males and females.

Plasma FSH/LH Concentration Test

• The plasma FSH/LH concentration test is utilized in postmenopausal women to assess ovarian function.
• Elevated levels indicate loss of feedback inhibition due to decreased ovarian activity.

Pulses of GnRH in Anterior Pituitary Gland

• Periodic pulses of hypothalamic GnRH are essential for stimulating the anterior pituitary gland to secrete LH and FSH.
• These pulses maintain reproductive function and hormonal balance.

Testosterone Synthesis in Males

• Luteinizing hormone (LH) stimulates the synthesis of testosterone in Leydig cells in males.
• Testosterone is vital for male reproductive functions and secondary sexual characteristics.

Estrogen and Inhibin Synthesis in Females

• Follicle-stimulating hormone (FSH) stimulates granulosa cells in females to synthesize estrogen and inhibin.
• These hormones are critical for ovarian function and menstrual cycle regulation.

GHRF's Effect on Somatotroph Cells

• GHRH enhances the activity of somatotroph cells, leading to increased production and release of growth hormone.
• It serves as a primary control mechanism for growth hormone dynamics.