Pituitary gland - functions and disorders | Master endocrinic gland

 PITUITARY GLAND

Glands are involved in the production and secretion of hormones. Pituitary gland is called as Hypophysis. It is the smallest gland among all the other glands, but it controls the all others glands. So, the pituitary gland is called as Master endocrinic gland. This pituitary gland produces 9 hormones.

POSITION:- It is located in sella turica, a depression in sphenoid bone and is attached to hypothalamus by a stalk. Anatomically it is divides as;

• Adenohypophysis (Anterior Pituitary) 7 hormones
• Neurohypophysis (Posterior Pituitary) 2 hormones

1. ADENOHYPOPHYSIS:- It is also called as Anterior Pituitary. It develops as an outgrowth of ectoderm called "Rakthe's poch", in the roof of buccal cavity. This anterior pituitary have 2 portions;

• Pars distalis
• Pars intermedia

ADENOHYPOPHYSIS

PARS DISTALIS:- In human, this pars distalis region of pituitary is commonly called as the anterior pituitary. This produce 6 types of hormones; they are:- 

• Human growth hormone (hGH)
• Thyroid-stimulating hormone (TSH)
• Adrenocorticotropic hormone (ACTH)
• Follicle-stimulating hormone (FSH)
• Luteinizing hormone (LH)
• Prolactin (PRL)

PARS INTERMEDIA:- In human, this pars intermedia is merged with pars distalis. It produce only 1 harmone; it is:- 

• Melanocyte-stimulating hormone (MSH)

Now, we see in detail about the 7 hormones produced by the anterior pituitary.

A. HUMAN GROWTH HORMONE (hGH):- This is also called as somatotropin. When this growth hormone is released, in response to this hGH, the cells in liver, skeletal muscles, cartilage, bone and other tissues secretes insulin-like growth factors(IGFs) that causes cells to grow and multiply. They increases uptake of amino acids into cells, accelerate protein synthesis and decreases the catabolism of proteins.  

B. THYROID-STIMULATING HORMONE (TSH):- This help to stimulate the synthesis and secretion of thyroid hormones from the thyroid gland.

C. ADRENOCORTICOTROPIC HORMONE (ACTH):- It helps to stimulate the synthesis and secretion of steroid hormones called glucocorticoids from adrenal cortex.

D. FOLLICLE-STIMULATING HORMONE (FSH):- In females, it stimualates growth and development of ovarian follicles. In males, along with FSH, androgens also regulate the spermatogenesis. FSH also induces sertoli cells to secrete inhibin.

E. LUTEINIZING HORMONE (LH):- In females, it induces the ovulation of fully matured follicles (graffian follicles) and maintains corpus luteum formed from the remnants of graffian follicles after ovulation. In males, LH is called interstitial cell stimulating hormone (ICSH) as it stimulates the interstitial cells of leydig in testes to synthesis androgens. LH and FSH stimulate gonadal activity and hence are called gonadotropins.

F. PROLACTIN (PRL):- It regulates the growth of mammary glands and used in the production of milk in them during lactation.

G. MELANOCYTE-STIMULATING HORMONE (MSH):- It acts on melanocytes (melanin-containing cells) and regulates the pigmentation of skin. The exact role in mammals is still unknown.

2.NEUROHYPOPHYSIS:- It is also called as Posterior Pituitary. It develops as an ectodermal out growth of hypothalamus. It is also called as Pars nervosa. It stores and regulates only 2 hormones;

• Oxytocin (OT) 
• Vasopressin (ADH - Anti-diuretic hormone)

NEUROHYPOPHYSIS

A. OXYTOCIN (OT):- It acts on smooth muscles of out body and stimulates their constriction. In females, it stimulates a vigorous contraction of uterus during the parturition and milk ejection from mammary glands after the child birth. Sounds of baby can cause a nursing mother to secrete oxytocin. So, the oxytocin plays a major role in parturition and lactation.

B. VASOPRESSIN (ADH):- It acts mainly at kidney and stimulates reabsorption of water and electrolyes, by distal tubules and there by reduces loss of water through urine (diuresis). Hence, it is called as ADH - Anti-diuretic hormone. In the absence of ADH, urine output increases from normal 1 to 2 liters to about 20 liters a day. ADH also decreases water loss through sweating and increases BP. Hence, it is called as vasopressin. Drinking alcohol often causes frequent and copious urination because alcohol inhibits secretion of ADH.

These are the 9 hormones released from the pituitary gland.

PITUITARY GLAND DISORDERS

There are 4 major pituitary gland disorders; they are:-

• Pituitary dwarfism
• Gigantism
• Acromegaly
• Diabetes insipidus

A. PITUITARY DWARFISM:- It is due to the hyposecretion of hGH during growth years slow down bone growth. The epiphyseal plates are lost before the normal height is reached. Other organs of body also fail to grow. The body proportions are child like. Hyposecretion of growth hormone in adults results in "Simmond's disease".

B. GIGANTISM:- It is due to the hypersecretion of hGH during childhood causes gigantism, an abnormal in length of long bones. The person grows very tall, but body proportions are about normal.

C. ACROMEGALY:- It is due to the hypersecretion of hGH during adulthood causes disproportionate gigantism called acromegaly. Altough hGH cannot produce further lengthening of long bones because epiphyseal plates are lost, the bones of hands, feet, cheeks, jaws thicken and other tissues enlarge. Eyelids, lips, tongue and nose enlarge.

D. DIABETES INSIPIDUS:- This is due to defects in ADH - Anti-diuretic hormone receptors (or) inability to secrete ADH. A common symptom of diabetes insipidus (insipid-tasteless) is excretion of large volumes of urine, resulting in dehydration and thirst.

These are the 4 major disorders of pituitary gland.