The Normal Growth Hormone Axis

These flashcards cover key concepts related to the growth hormone axis, including secretion mechanisms, physiological actions, and related disorders.

What is the primary type of cell that secretes growth hormone (GH)?

Somatotrophs in the anterior pituitary.

Describe the chemical nature of GH.

GH is a polypeptide and a single chain protein.

What is the blood concentration level of growth hormone in adults?

Approximately 3 ng/ml.

What regulates the secretion of growth hormone?

GHRH stimulates and somatostatin inhibits GH secretion.

What are the two forms of GH?

Major form (22 kDa) and minor form (20 kDa).

What is the role of IGF-1 in relation to GH?

IGF-1 mediates many of the effects of GH.

How does growth hormone affect fibroblast transformation?

GH promotes fibroblast transformation and growth.

Which mechanism is responsible for GH-induced insulin resistance?

The increase in free fatty acid flux from adipose tissue.

What happens to GH receptors after occupancy?

They dimerize and trigger intracellular signaling.

What is Laron syndrome characterized by?

Insensitivity to growth hormone due to mutations in GHR.

What hormones stimulate GH secretion?

Arginine, thyroid hormones, and gonadal hormones.

What inhibits GH secretion?

Cortisol, glucose, and free fatty acids.

What does IGF-1 stand for?

Insulin-like Growth Factor 1.

What action does GH have on metabolism?

Decreases glucose metabolism and increases lipolysis.

What is one of the consequences of excessive GH in adults?

Acromegaly.

Describe the direct physiological action of GH.

It promotes protein synthesis and growth.

What is the role of SOCS in GH signaling?

SOCS proteins terminate the growth hormone signal cascade.

How can GH levels be measured clinically?

Using techniques like ELISA and bioassays.

Describe one disorder associated with hyposecretion of GH.

Dwarfism in children.

What is the connection between aromatase and growth plate closure?

Aromatase converts androgens to estrogens, causing growth plate fusion.