Harmones of Anterior Pituitary

OTHER HORMONES OF ANTERIOR PITUITARY

Thyroid-stimulating Hormone (TSH)

TSH is necessary for the growth and secretory activity of the thyroid gland. It has many actions on the thyroid gland.

Adrenocorticotropic Hormone (ACTH)

ACTH is necessary for the structural integrity and the secretory activity of adrenal cortex. It has other functions also.

Follicle-stimulating Hormone (FSH)

Follicle-stimulating hormone is a glycoprotein made up of one α-subunit and a β-subunit. The α-subunit has 92 amino acids and β-subunit has 118 amino acids. The half-life of FSH is about 3 to 4 hours.



Actions of FSH

In males, FSH acts along with testosterone and accelerates the process of spermeogenesis.

In females FSH:

1. Causes the development of graafian follicle from primordial follicle

2. Stimulates the theca cells of graafian follicle and causes secretion of estrogen.

3. Promotes the aromatase activity in granulosa cells, resulting in conversion of androgens into estrogen.

Luteinizing Hormone (LH)

LH is a glycoprotein made up of one α-subunit and one β-subunit. The α-subunit has 92 amino acids and

β-subunit has 141 amino acids. The half-life of LH is about 60 minutes.

Actions of LH

In males, LH is known as interstitial cell-stimulating hormone (ICSH) because it stimulates the interstitial

cells of Leydig in testes.

In females, LH:

1. Causes maturation of vesicular follicle into graafian follicle along with follicle-stimulating hormone

2. Induces synthesis of androgens from theca cells of growing follicle

3. Is responsible for ovulation

4. Is necessary for the formation of corpus luteum

5. Activates the secretory functions of corpus luteum.

Prolactin

Prolactin is a single chain polypeptide with 199 amino acids. Its half-life is about 20 minutes. Prolactin is

necessary for the final preparation of mammary glands for the production and secretion of milk.

Prolactin acts directly on the epithelial cells of mammary glands and causes localized alveolar hyperplasia.

β-lipotropin

β-lipotropin is a polypeptide hormone with 31 amino acids. It mobilizes fat from adipose tissue and promotes lipolysis. It also forms the precursor of endorphins. This hormone acts through the adenyl cyclase

POSTERIOR PITUITARY OR NEUROHYPOPHYSIS

PARTS

Posterior pituitary consists of three parts:

1. Pars nervosa or infundibular process

2. Neural stalk or infundibular stem

3. Median eminence.

Pars tuberalis of anterior pituitary and the neural stalk of posterior pituitary together form the hypophyseal

stalk.

HISTOLOGY

Posterior pituitary is made up of neural type of cells called pituicytes and unmyelinated nerve fibers.

Pituicytes

Pituicytes are the fusiform cells derived from glial cells. These cells have several processes and brown pigment granules. Pituicytes act as supporting cells and do not secrete any hormone.

Unmyelinated Nerve Fibers

Unmyelinated nerve fibers come from supraoptic and paraventricular nuclei of the hypothalamus through the pituitary stalk.

Other Structures

Posterior pituitary also has numerous blood vessels, hyaline bodies, neuroglial cells and mast cells.

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