8
Prolactin
Prolactin stimulates the secretion of milk immediately after delivery by inducing
direct effect on the breast. Prolactin initiates and maintains lactation along with
estrogen and progesterone. Hypothalamus releases dopamine into hypothalamohypophyseal portal system, thereby inhibiting its release. Release of prolactin releasing hormone from the hypothalamus can erratically enhance prolactin secretion, for
example, whenever the infant sucks on breast [6].
Thyroid Stimulating Hormone (TSH)
Hypothalamus secretes the thyrotropin releasing hormone and transports it through
the hypothalamohypophyseal portal system to the pituitary gland, thereby producing and releasing TSH from the anterior pituitary. The hypothalamus can also inhibit
TSH secretion by releasing somatostatin, just as inhibition of growth hormone (GH)
happens. Free T4 as well as free T3 in blood stream negatively respond/feedback the
pituitary and hypothalamus in order to control the concentration of these circulating
hormones.
Fig. 1.3 Negative feedback regulation of secretion of hormones by the anterior lobe of the pituitary gland
A. Ahsan et al.