Prolactin is a vital hormone synthesized mainly by the pituitary gland located within the brain and it is also scientifically referred to as PRL, lactotropin, luteotropic hormone, LTH and lactogenic hormone. Although this biochemical substance is produced in both men and women and is involved in numerous cellular functions in the system, the chief role of prolactin is inducing lactation processes i.e. production of milk in females post childbirth. Moreover, during pregnancy, prolactin prompts the development of female mammary glands situated internally in the breast tissues.
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In the human body, prolactin is chiefly synthesized in the frontal regions of the pituitary gland within the brain i.e. anterior pituitary gland, by specialised cells known as lactotroph cells or lactotrophic cells. After the formation of prolactin, the signalling hormone is stored in the lactotroph cells and distributed into the bloodstream when required, primarily for pregnancy and lactation purposes. Besides the pituitary gland, prolactin is also produced in other portions of the brain, as well as the breasts, uterus, prostate, immune cells, adipose tissue, skin and performs key tasks in boosting immunity, regulating glucose and fat metabolism.
The levels of prolactin in the human body, both in men and in women, are principally regulated by two central biochemical components – dopamine, a neurotransmitter responsible for positive emotions which operates as a hormone and estrogen, a key hormone for female reproductive functions. This biochemical prolactin control mechanism is more significant in females, especially in the pregnancy and lactation phases. Dopamine works by reducing the synthesis and release of prolactin, implying that higher the dopamine levels, lower will be the amount of prolactin circulating in the bloodstream. Estrogen increases the formation of prolactin in the pituitary gland, in addition to the secretion of the hormone in blood flow.
Also Read: Estrogen: Structure, Crucial Functions, Adverse Effects
Owing to the critical roles of prolactin in women during pregnancy and lactation, it is important to understand the key biological operations of prolactin and the negative implications of imbalanced levels of this hormone in the human body.
Prolactin And Its Structure:
The presence of prolactin was discovered and confirmed in humans by the recognised Canadian endocrinologist and medical researcher, Henry George Friesen, in the year 1970.
Prolactin displays three biological structures within the human system, known as little prolactin, big prolactin and big big prolactin, with only little prolactin being present in major proportions.
The structure of the most prevalent form of prolactin i.e. little prolactin is essentially a peptide hormone, entailing a single-chain protein with a sequence of 198 amino acids and having a molecular weight of 22-kDa (Kilo Daltons). This is the form of prolactin that carries out pivotal roles in pregnancy and lactation.
Big prolactin, with a molecular mass of 48-kDa and big big prolactin, weighing 150-kDa, do not portray any significant biological activity within the human body.
Vital Functions Of Prolactin:
The fundamental biological functions of prolactin comprise:
- Enlargement of mammary glands in breast tissues of pregnant women, to assist in the synthesis and storage of breast milk postpartum for the newborn child.
- Augmenting lactation processes in women after delivery of the baby, by stimulating the generation of milk proteins, healthy lipids, lactose in the lactating mammary gland to ensure healthy nourishment for the infant.
- Bolstering immunity in both men and women, by positively influencing the immune cells, particularly lymphocytes and macrophages in the blood, spleen and thymus.
- Controlling glucose uptake by cells and fat/lipid metabolism, by triggering the activity of various enzymes involved in the biochemical cycles of macromolecules.
Adverse Effects:
In some instances, the levels of prolactin being synthesized in the pituitary gland of the brain or circulating in the bloodstream may be very high or rather low compared to normal. These situations cause certain health anomalies and discomforting symptoms.
High Prolactin Levels:
The ailment resulting from excess prolactin levels in the body is termed hyperprolactinemia. The primary causes of this condition consist of pregnancy, the hampered activity of the thyroid gland, hormones, consuming prescription drugs that lower the function of the neurotransmitter and hormone dopamine in the body.
Hyperprolactinemia gives rise to irregular menstrual cycles/periods, estrogen deficiency in females and low testosterone levels in men. Treatment usually involves prescribed medicines to correct the hormonal levels of dopamine and prolactin.
Low Prolactin Levels:
Hypoprolactinemia arises due to very low levels of prolactin in the body. It is a rare health condition that is generally caused by an underactive pituitary gland in the brain.
The main symptoms of hypoprolactinemia are reduced production of breast milk in women post-pregnancy and decreased immunity to combat common infections and diseases such as cough, cold, fever.
Conclusion:
Prolactin is a very essential hormone for women in the pregnancy and lactation stages, for healthy breast milk production, enhanced lactating abilities, aside from elevated immunity and controlled glucose, lipid metabolism. It is hence imperative to ensure the proper levels and mechanisms of this hormone, to prevent illnesses from high or low prolactin levels and uplift overall health.
