Growth Hormone Physiology

GH is a hormone produced by the pituitary gland that plays a crucial role in growth development.

GH indirectly stimulates growth by stimulating the liver to produce somatomedins (IGF-1 and IGF-2), which directly act on bone and protein metabolism.

IGF-1 (somatomedin C) is a key player that directly stimulates growth by promoting bone cell differentiation and protein synthesis. It is released slowly from plasma proteins, enabling prolonged effects.

IGF-2 plays a vital role during fetal development, contributing to the growth of the fetus.

GH promotes calcium absorption in the intestines, providing essential minerals for bone mineralization and growth.

GH stimulates muscles to increase in size and strength through a process called sarcomere hypertrophy.

Excessive GH secretion can lead to gigantism in children, as their long bones continue to grow beyond normal limits.

In adults, excess GH can cause acromegaly, characterized by thickening of bones in the hands, feet, and face.

Growth Hormone (GH) is a protein secreted by somatotropes in the anterior pituitary gland. It's a single-chain polypeptide with 191 amino acids and a molecular weight of 21,500. GH levels are higher in children and adolescents than adults.

GH is transported in the blood by GH-binding proteins (GHBPs). It has a half-life of about 20 minutes and is degraded in the liver and kidney.

GH's primary role is to promote general body growth. It achieves this by increasing cell size (hypertrophy) and stimulating cell division (mitosis), leading to the development of more cells and specialized tissues.

GH increases protein synthesis by facilitating amino acid transport into cells, enhancing RNA translation, promoting DNA transcription, and decreasing protein breakdown.

GH increases the release of insulin from the pancreas. Insulin has an anabolic effect on proteins, further promoting growth.

GH mobilizes fat from adipose tissue, providing energy to allow for protein sparing. High levels of GH can lead to the release of acetoacetic acid from the liver, resulting in ketosis.

GH promotes glucose conservation by decreasing peripheral glucose utilization. It also increases glycogen deposition and reduces glucose uptake by cells, leading to a diabetogenic effect.

GH's diabetogenic effect refers to its ability to decrease glucose uptake by cells, leading to a rise in blood sugar levels, similar to the effects of diabetes.

A condition where the pituitary gland produces too much growth hormone (GH) in adults, after the bones have stopped growing. This leads to abnormal growth, particularly in the hands, feet, and face.

A tumor in the pituitary gland that produces excessive GH, leading to symptoms of acromegaly like enlarged hands and face.

A characteristic feature of acromegaly where the face appears broadened with prominent features like a protruding jaw and thickened lips.

A condition resulting from a deficiency of growth hormone (GH) in children, leading to stunted growth.

A non-functioning tumor in the pituitary gland that compresses and damages the normal cells producing GH, leading to dwarfism.

A condition where the pituitary gland fails to produce sufficient amounts of all its hormones, including GH, leading to dwarfism and other symptoms of hormone deficiency.

This condition prevents the pituitary gland from releasing growth hormone (GH) due to the negative effects of somatostatin and dopamine on GH production.

Dwarfism is characterized by a maximum height of around 3 feet in adults, while the body proportions remain relatively normal.

The growth hormone receptor, located primarily on liver cells, is a transmembrane receptor that binds to Growth Hormone (GH), forming a complex that triggers the release of somatomedins. These somatomedins then carry out the actions of GH.

Hypoglycemia, fasting, starvation, exercise, stress, trauma, and the initial stages of sleep all stimulate GH secretion. This means that GH production increases in response to these conditions.

Hyperglycemia (high blood sugar), an increase in free fatty acids in the blood, and later stages of sleep inhibit GH secretion. These conditions signal the body that resources are readily available.

The hypothalamus, a key brain region, regulates GH secretion via three hormones. GHRH (Growth Hormone-Releasing Hormone) increases GH secretion by stimulating the anterior pituitary. GHRP (Growth Hormone-Releasing Polypeptide) promotes the release of GHRH from the hypothalamus and GH from the pituitary. GHIH (Growth Hormone-Inhibitory Hormone), also known as somatostatin, reduces GH secretion.

Gigantism is a condition resulting from excessive GH secretion during childhood or pre-adulthood, before the bones have completely fused. It is often caused by a tumor in the anterior pituitary gland.

The symptoms of Gigantism include a remarkably tall stature due to disproportionately long limbs. Other symptoms may include hyperglycemia (high blood sugar), glycosuria (sugar in urine), and potentially impaired vision.

Individuals with Gigantism might develop pituitary diabetes or diabetes mellitus due to the body's inability to regulate blood sugar effectively. Another potential symptom is visual impairment, potentially caused by pressure on the optic nerve.

The anterior lobe of the pituitary gland secretes tropic hormones, which control the activity of other endocrine glands.

The posterior pituitary releases oxytocin and vasopressin, both crucial for various bodily functions.

The pituitary gland plays a vital role in regulating downstream glands and influencing various peripheral organs and tissues.

The pituitary gland releases hormones like FSH, LH, and prolactin, which are crucial for reproductive processes and lactation.

Growth hormone (GH) is secreted in bursts and its release is influenced by hypothalamic factors and feedback inhibition.

GH promotes growth, protein synthesis, and influences carbohydrate and fat metabolism. It helps the body react to stressful conditions.

Many of GH's actions are mediated through its ability to stimulate the production of IGF-I, which directly facilitates growth.

Growth is a complex process involving multiple hormones, including GH, IGF-I, and others. The consequences of their overproduction or underproduction depend on whether it occurs before or after puberty.