Pituitary Gland

 Pituitary Gland

It consists of three lobes, anterior, middle and posterior.

Location: Floor of diencephalons and attached to the hypothalamus by a stalk to form

hypothalamic – pituitary system.

(a) Anterior lobs of Pituitary: It possesses acidophils (a- cells), basophils (b-cells) and

chromophobes (precursors of other two). Acidophils produce two hormones (GH and

LTH) while basophils secrete five hormones (TSH, Lipotropin, ACTH, FSH, LH).

(i) Somatotropin or Growth Stimulating Hormone (GH)

Functions: Stimulates growth by accelerating the protein synthesis and retention

of calcium.

Effect of hyposecretion: Less secretion of GSH leads to dwarfism and acromicria in adults.

Effect of Hypersecretion: Gigantism. Due to excess secretion of GSH during

childhood. Acromeagly in adults.

(ii) Prolactin/ Lactogenic or Luteotrophic Hormone (LTH)– Proteinaceous

hormone (often included under gonadotrophins) that stimulates development of

mammary glands during pregnancy and lactation after childbirth. It is also called

maternity hormone.

(iii) Lipotropin or Adipokinetic Hormone– The hormone stimulates liberation of

fatty acids from stored fats.

(iv) Gonadotropins: The hormones, which regulate the sexual activity of gonads,

and other structures of the body. They include:

Follicle Stimulating Hormone (FSH)

Functions: Stimulation of testes in male to form the sperms from the

seminiferous tubules: In females, the FSH stimulates ovary for the

maturation of ovation follicle. Here, it also stimulates the follicular cells to

secrete estrogen. The latter is responsible for the secondary sexual

characters in female.

Effect of hyposecretion: Failure of gamete formation from the gonads.

2. Intestinal Cells Stimulating Hormone (ICSH) in males.

Functions Stimulates the interstitial or Leydig’s cells or testis to produce testosterone. The latter brings about secondary sexual characters of male.

Effect of hyposecretion: Impaired development of the external genitali

.

3. Leutinizing hormone in females (LH) (or Lutropin).

Functions: Release of ovum from ovary (ovulation); formation of corpus luteum and the secretion of progesterone from corpus luteum.

Effect of hyposecretion: Sterility in females.

(v) Thyroid Stimulating Hormone (TSH)

Function: Production of thyroid hormones from thyroid gland

(vi) Adrenocortiocotropin Hormone (ACTH):

Function: Brings about the production and release of hormones from adrenal

cortex.

(b) Intermediate lobs of pituitary

Hormone: Melanocytes stimulating hormone (MSH)

Function: May be connected with pigment maintenance in hair, pregnancy related

skin pigmentation

.

(c) Posterior lobs of pituitary

Hormones

(i) Oxytocin (Pitocin): Stimulation of uterine contraction during child birth. Stimulation of milk flow by mammary glands under the control of Prolactin or LTH.

(ii) Vasopressin (Pitressin, ADH): Influences water balance by reducing output of urine by reabsorption of water from nephric filtrate in DCH and CT. Also, causes arteriole constriction, raise blood pressure and causes contraction of several smooth muscles like those of intestine, gall bladder, urinary bladder etc.

Hyper secretion

Causes Diabetes insipidus (Drinker’s disease) It is hormonal abnormality of polyuria

(excessive urine) or micturating dilute urine (hypotonic, sugar-free) several times a

day.

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