Growth Hormone and Its Effects

Growth Hormone-Releasing Hormone (GHRH) from the hypothalamus stimulates the production of growth hormone.

The presence of thyroid hormone is necessary for normal levels of growth hormone.

Cretinism is a condition caused by the absence of thyroid hormone. It can lead to stunted growth.

GH's half-life is short, meaning it's quickly broken down in the body.

IGF-1 (Insulin-like Growth Factor 1) is a primary inhibitor of GH secretion due to its longer half-life and binding proteins.

Ghrelin, an incretin hormone released from the gut, stimulates GH secretion.

Stress (physical or psychological), hypoglycemia (low blood sugar), amino acids, and trauma can all stimulate GH secretion.

GH levels are higher in children compared to adults, with a peak during puberty.

GH secretion declines as people age.

Adults continue to produce GH, but at lower levels, primarily to maintain metabolism.

A hormone produced by the pituitary gland that plays a crucial role in growth and development.

A group of proteins primarily produced by the liver that mediate the growth-promoting effects of GH.

GH stimulates the production of IGFs, which directly promote the growth and division of chondrocytes, leading to bone lengthening.

GH stimulates lipolysis, the breakdown of fat, increasing the availability of fatty acids for energy.

GH enhances the production of proteins in muscles, leading to increased muscle mass and strength.

GH influences the activity of osteoblasts, the cells responsible for bone formation and remodeling.

GH promotes protein synthesis in various tissues, contributing to overall growth and development.

GH decreases the body's use of glucose, promoting the utilization of fat as an energy source.

The liver is a key target for GH, releasing IGFs in response to its stimulation.

The effects of GH on stature are largely mediated by IGFs, which directly stimulate chondrocyte activity at the growth plates.

Besides the liver, other cell types, such as those found in bone, can also release somatomedin in response to GH.

Adult stature requires GH for proper growth.

Pituitary dwarfism in childhood is caused by a deficiency of growth hormone (GH).

Laron dwarfism is a condition where the body is unable to respond to GH due to a problem with the GH receptor, unlike pituitary dwarfism, which involves GH deficiency.

Gigantism is a condition characterized by excessive GH production during childhood, resulting in an exceptionally tall stature.

Acromegaly is caused by overproduction of GH in adulthood, unlike gigantism, which occurs in childhood.

GH plays a role in facilitating the genetic expression of growth potential.

GH influences approximately ±30% of the genetic growth potential.

In the fed state, GH and IGF-1 promote anabolic growth by stimulating protein synthesis, cell growth, and tissue repair.

During fasting, GH mobilizes fat for energy while preserving glucose and protein levels.

Prolactin (PRL) is a hormone secreted by lactotropes, cells found in the anterior pituitary gland.

Lactotrope cells are not part of a typical endocrine axis, meaning they don't directly respond to a tropic hormone from the hypothalamus.

The hypothalamus normally inhibits the release of prolactin.

When the pituitary stalk is disrupted, prolactin secretion increases significantly.

Prolactin secretion is regulated by a neuro-endocrine feedback loop, where the hypothalamus signals to the anterior pituitary, influencing prolactin release.

The ejection of milk from the mammary gland is controlled by oxytocin.

Prolactin is responsible for the production and secretion of milk by the mammary gland.

The final stage of epithelial cell arrangement, involving tight junctions and the basement membrane, takes place after the delivery of the placenta and the subsequent decrease in pregnancy hormones.

Nursing immediately after birth is critical to establishing lactation. It ensures high levels of prolactin to stimulate milk production.

The production of milk in the matured mammary gland depends on continuous stimulation by prolactin.