Problem 27 - Objective Biology for NEET

Question

Which of the following hormones regulate the growth of the mammary glands and formation of milk? (a) \(\mathrm{GH}\) (b) TSH (c) Prolactin (PRL) (d) ACTH

Step-by-Step Solution

Answer

The hormone that regulates the growth of the mammary glands and formation of milk is Prolactin (PRL).

Step 1: Identify the roles of each hormone

GH stands for Growth Hormone, which is primarily responsible for cell growth and regeneration. TSH is Thyroid Stimulating Hormone, it stimulates the thyroid gland to produce thyroxine (T4), and then triiodothyronine (T3), which stimulates the metabolism of almost every tissue in the body. Prolactin (PRL) has many effects, but its primary role is to promote lactation (milk production). ACTH is Adrenocorticotropic Hormone, and it stimulates the adrenal glands to produce and release corticosteroids.

Step 2: Match the function to the question

The question seeks to find the hormone that regulates the growth of the mammary glands and formation of milk. From the hormone functions identified in the prior step, that role best fits Prolactin (PRL).

Key Concepts

Mammary glands growth

Mammary glands play a crucial role in the reproductive system of mammals. They are specifically involved in producing milk, which is essential for the nourishment of the offspring. The growth of these glands is primarily influenced by hormonal activity. During puberty, estrogen initiates the development of the duct system within the mammary glands. As a female approaches reproductive age, further hormonal interactions prepare the gland tissue for potential milk production. Progesterone and other hormones help stimulate the growth of lobular and alveolar structures, which are key components of mammary glands. This growth and development are essential to ensure that the glands are functional during lactation.

Lactation

Lactation is the process of milk production, and it is a vital post-pregnancy function that allows for the feeding of newborns. Prolactin (PRL) plays a central role in this process by stimulating milk secretion from the epithelial cells within the alveoli of the mammary glands.

There are several stages involved in lactation:

• Milk Synthesis: Prolactin stimulates the synthesis of milk components, including water, lipids, proteins, and lactose, beginning late in pregnancy.
• Milk Ejection: The hormone oxytocin induces the contraction of muscles around the alveoli, pushing milk through the ducts to the nipple for release.
• End of Lactation: When the production of milk ceases, either through hormonal changes or a reduction in nursing stimulus, the glands gradually return to a non-lactating state.

Lactation ensures that newborns receive essential nutrients and antibodies, crucial for their early development and immune protection.

Hormonal regulation

The hormonal regulation of mammary glands and lactation is a complex yet well-coordinated system. Hormones act as messengers, directing many physiological processes.

Some key hormones involved include:

• Estrogen: Responsible for the initial development of mammary ductal structures during puberty. It continues to play a role during each menstrual cycle by stimulating ductal growth.
• Progesterone: Works alongside estrogen to develop the lobular and alveolar tissues within the glands, preparing them for milk production.
• Prolactin (PRL): Directly stimulates milk production post-pregnancy within the mammary glands and is crucial for maintaining milk supply.
• Oxytocin: Facilitates the release of milk by causing contractions in the muscles around the alveoli, leading to milk ejection or "let-down."

Understanding these hormonal processes is essential for comprehending how the body prepares and executes the complex tasks required for nurturing young mammals. Prolactin, among these, is particularly significant for its direct role in milk synthesis.