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A Handbook of Biology

6.

Luteinizing hormone (LH):



Stimulates gonadal activity. In males, it stimulates synthesis and

secretion of androgens from testis. In females, it induces ovulation

and maintains the corpus luteum.

Pars intermedia: In human, it is almost merged with pars distalis. It produces

Melanocyte stimulating hormone (MSH) which acts on melanocytes to

regulate skin pigmentation.

B. ÑËÜRØHÝPØPHÝSÏS (PÅRS ÑËRVØSÅ/ PØSTËRÏØR PÏTÜÏTÅRÝ)

It stores oxytocin & vasopressin from hypothalamus. (NEET II 2016)

Oxytocin (Birth hormone): Contracts smooth muscles. In females, it

stimulates contraction of uterus during child birth, and milk ejection

from the mammary gland.

Vasopressin

or

Anti-diuretic

hormone

(ADH):

Stimulates

reabsorption of water & electrolytes by DCT of kidney and thereby

reduces diuresis (loss of water through urine).

Deficiency of ADH results in diminished ability of the kidney to conserve

water. It leads to water loss and dehydration. This is called diabetes

insipidus.

3. PÏÑËÅL GLÅÑD



It is located on dorsal side of forebrain. Secretes melatonin.



Regulates diurnal (24-hour) rhythm of body (AIPMT 2014). E.g. sleep-

wake cycle, body temperature etc. Influences metabolism, pigmentation,

menstrual cycle and defense capability.

4. THÝRØÏD GLÅÑD



Largest endocrine gland. It includes 2 lobes on either side of the trachea.

The lobes are interconnected with isthmus (a connective tissue). Thyroid

gland is made of follicles & stromal tissues. Follicular cells secrete the

following hormones: