3 Ways to Control Secretion of Hormones | Mammalian Endocrinology

The following points highlight the three ways to control secretions of hormones. The three ways are: 1. Neural Control 2. Endocrine Control 3. Feedback Control.

Secretion of Hormones: Way # 1. Neural Control:

Some endocrine secre­tions are solely controlled by nerve im­pulses. Secretion of adrenal medullary hormones secretion of neuro-hypophysial hormones and various releasing hor­mones of hypothalamus are under this category.

For instance, in mammals, the act of suckling of baby stimulates tactile receptors in the nipple of mother and this impulse stimulates hypothalamic cells through sensory nerve and spinal cord. Latter, hypothalamic neuro-secretion stimulates neurohypophysis for secretion of oxytocin. Oxytocin helps in secretion of milk.

Secretions of Hormones: Way # 2. Endocrine Control:

Some endocrine se­cretions are controlled by other endo­crine glands. For instance, different re­leasing hormones of hypothalamus con­trol the secretion of anterior pituitary hormones. TSH-RH of hypothalamus controls the secretion TSH from anterior pituitary.

Similarly, TSH and ACTH se­cretion of anterior pituitary stimulate thy­roid gland and adrenal cortex respec­tively for secretion of thyroid hormone and adrenal cortical hormone.

Secretions of Hormones: Way # 3. Feedback Control:

The process of inhib­iting or stimulating the first step by the final step in a hormonal reaction path­way, is called feedback regulation. The secretion of a hormone may be stimu­lated or inhibited by the feedback effect of some other hormone or metabolite.

This feedback control can be divided into two ways:

(a) Negative feedback mechanism:

In this type, rising concentration of a hormone inhibits the release of sec­ond hormone from other gland, called negative feedback control (Fig. 3.2).

Example:

(i) Pineal hormone is anti-gonadotropic in nature. Increased secre­tion of pinealin of pineal gland inhibits the anterior pituitary for secretion of gonadotropin.

(ii) High secretion of Cortisol of the adrenal cortex inhibits the secre­tion anterior pituitary corticotrophin.

(b) Positive feedback mechanism:

In this mechanism, rising concentration of a hormone acts on another gland to release second hormone, which further stimulates the first hormone, called positive feedback mechanism (Fig. 3.3).

Example:

At pre-ovulatory phase, a gonadal hormone estrogen increases the release of pituitary LH, which in turn stimulates ovarian estrogen pro­duction. Thus estrogen and LH lev­els go on increasing continuously.