Growth Hormone Production and Regulation

What hormone stimulates the release of growth hormone (GH)?

At what stage of life is the secretion of growth hormone typically at its peak?

Which of the following hormones negatively regulates the production of growth hormone?

What condition results from abnormal hyper-secretion of growth hormone in childhood?

What role does Insulin Growth Factor 1 (IGF-1) play in the action of growth hormone (GH)?

What is the role of Janus Kinase 2 (JAK2) in the GH signaling pathway?

In which condition is mecasermin particularly beneficial?

What major action does growth hormone (GH) have related to body composition?

Which process occurs when GH interacts with its receptors?

What is the primary clinical effect of Tesamorelin?

What is a potential side effect of using mecasermin?

What physiological role does growth hormone (GH) play during childhood?

What role does octreotide play in the treatment of GH-related conditions?

What is pegvisomant used for?

What is the primary reason for administering GH releasing hormones?

Which scenario illustrates a condition of GH deficiency?

Growth Hormone (GH) Production and Regulation

GH and prolactin (PRL) are produced by specific cells in the anterior pituitary, regulated by the hypothalamus.
GH release is stimulated by growth hormone-releasing hormone (GHRH) and Ghrelin, but inhibited by somatostatin (SST), GH itself, and insulin-like growth factor 1 (IGF-1).
GH production is pulsatile, highest during sleep, stimulated by GHRH and Ghrelin, inhibited by SST, GH, and IGF-1.
GH production is high in infancy, peaks during puberty, and decreases in adulthood.
GH binds to cell-surface GH receptors (GHR) and activates them, stimulating the production of IGF-1, mainly by the liver.
Elevated GH and IGF-1 levels induce negative feedback loops, inhibiting further GH secretion.

GH Actions and Effects

GH promotes longitudinal bone growth, and increases glycolysis and body fat storage, supporting muscle mass, immune function, cardiovascular health, and nervous system well-being.

GH Hypersecretion: Leads to gigantism in childhood and acromegaly in adulthood, characterized by abnormal longitudinal bone growth.
GH Deficiency/Signal Disruption: Causes short stature, or rare syndromes.

GH Receptors

Similar to cytokine receptors, lacking intrinsic kinase activity.
Rely on the recruitment of non-receptor tyrosine kinase JAK2 for activation.

GH Receptor Activation Pathway

GH binding activates JAK2 within the receptor.
JAK2 phosphorylates downstream targets, including STAT5.
STAT5 dimerizes and enters the nucleus, modulating gene transcription.
Genes involved in growth, metabolism, and sex dimorphism are affected.

Replacement Therapy (Somatotropin): Uses GH analogues to treat GH deficiency.
GH Receptor Bypass: In cases of receptor dysfunction, IGF-1 replacement (mecasermin) is used, aiming to mimic the effects of GH.
GH Release Stimulation (Tesamorelin): Synthetic GHRH analogue mimicking hypothalamic function, reduces visceral fat accumulation.

This quiz covers the production and regulation of growth hormone (GH), including its stimulation and inhibition mechanisms, actions, and related pathologies. Explore how GH functions in promoting growth and maintaining health across different life stages.