(1) In the hypothalamus, there are several groups of neurosecretory cells which form different nuclei. 

(2) These hypothalamic nuclei are supraoptic, paraventricular, dorso-median and ventromedian nuclei. These neurosecretory cells produce releasing and inhibiting factors.

(3) The hypothalamic neurohormones regulating the release of pituitary hormones are called releasing factors. The following are some of J the important releasing factors:

• CRF or corticotropin releasing factor or ACTH releasing factor releases secretion of Adrenocorticotropin hormone (ACTH). 
• TRF or TSHRF (Thyroid stimulating hormone releasing factor) stimulates release of TSH.
• FSH RF (Follicle stimulating hormone ; releasing factor) stimulates release of FSH. GHRF (Growth hormone releasing factor) 
• GHRIF (Growth hormone release inhibiting factor) act on release and regulation of growth hormone. 
• PRF (Prolactin releasing factor) and PRIF ; (Prolactin release inhibiting factor) act on release and regulation of prolactin. 
• MSHRF (Melanocyte stimulating hormone releasing factor) and MSH RIF (Melanocyte stimulating hormone release inhibiting factor) act on release and regulation of MSH.