Growth Hormone Flashcards

Flashcards about Growth Hormone, its regulation, and related deficiencies, based on lecture notes.

What hormones are produced by the anterior lobe of the pituitary gland?

ACTH, TSH, LH, FSH, GH, and Prolactin

What hormones are produced by the posterior lobe of the pituitary gland?

ADH and Oxytocin

What is another name for growth hormone?

Somatotropin

What part of the brain secretes growth hormone-releasing hormone?

Hypothalamus

What is the hypophyseal portal system?

A network of capillaries linking the hypothalamus to the anterior pituitary gland

What cells in the anterior pituitary release growth hormone?

Somatotroph cells

How is growth hormone releasing hormone typically released?

In a pulsatile manner throughout the day, peaking one hour after falling asleep, and in response to internal/external stimuli

What internal stimulus causes the hypothalamus to secrete growth hormone releasing hormone?

Hypoglycemia (low blood sugar)

What external stimulus causes the hypothalamus to secrete growth hormone releasing hormone?

Exercise (via adrenaline secretion from adrenal glands)

How do estrogen and testosterone affect growth hormone release?

Increased levels of estrogen and testosterone during puberty stimulate the hypothalamus to release growth hormone releasing hormone.

What are the three negative feedback loops that control growth hormone release?

1. Increased levels of GHRH signal the hypothalamus to stop making more. 2. Growth hormone reaching tissues causes them to make somatomedins, which signal the anterior pituitary to stop producing growth hormone. 3. Growth hormone and somatomedins together signal the hypothalamus to produce somatostatin.

What is somatostatin, and what does it do?

Also called growth hormone-inhibiting hormone, it blocks GHRH from acting on somatotroph cells in the pituitary, inhibiting growth hormone secretion and inhibiting other hormones in the GI tract

How does growth hormone stimulate growth?

Directly and indirectly via direct stimulation of cellular metabolism, and indirectly via the release of somatomedin C (IGF-1).

What are the direct effects of growth hormone?

Lipolysis in adipose tissue, gluconeogenesis and glycogenolysis in the liver, and increased insulin resistance in tissues

What are the indirect effects of growth hormone?

Stimulates the release of somatomedin C (IGF-1) in the liver, skeletal muscles, bones, and kidneys.

What is the function of IGF-1?

Promotes cellular metabolism, prevents cell death, increases the rate of cell division and differentiation, stimulates amino acid uptake in muscles, and stimulates growth in length of long bones.

How does IGF-1 affect bone growth?

It acts on the epiphyseal cartilage (growth plates), stimulating osteoblasts and chondrocytes, boosting growth during puberty.

What are the main regulators of growth hormone release?

Growth hormone releasing hormone (GHRH) increases its release, and somatostatin inhibits its release.

What are the direct and indirect effects of growth hormone in promoting overall body growth?

Direct effects include lipolysis, gluconeogenesis, and glycogenolysis. Indirect effects primarily occur in muscles and bones.

What are the main problems associated with growth hormone deficiency?

Impaired overall growth, muscle mass development, protein synthesis, and carbohydrate/lipid metabolism.

What is the hypothalamic-pituitary axis?

The hypothalamus secretes growth hormone releasing hormone, which travels to the anterior pituitary and stimulates it to secrete growth hormone. Growth hormone then travels via the blood to various target tissues in the body to stimulate growth.

How does exercise affect growth hormone release?

Exercise causes the adrenal glands to secrete epinephrine, which stimulates the hypothalamus to release growth hormone releasing hormone.

How do high levels of growth hormone and growth hormone releasing hormone in the blood regulate the hypothalamic pituitary axis?

They signal the hypothalamus to stop secreting more growth hormone releasing hormone, creating a negative feedback loop.

How do somatomedins regulate the hypothalamic pituitary axis?

They inhibit growth hormone secretion from the anterior pituitary and stimulate somatostatin release, creating a negative feedback loop.

What is Diabetogenic effect?

Growth hormone increases insulin resistance, decreasing insulin's ability to move glucose into cells, leading to increased glucose levels, which stimulates the release of more insulin.

How does growth hormone stimulate muscle growth?

It stimulates amino acid uptake into the muscle cells, which helps with protein production.

What is the role of insulin-like growth factor (IGF) in growth hormone function?

IGF mediates many of the effects of growth hormone, such as promoting growth, cell reproduction, and regeneration.

What are some common genetic causes of growth hormone deficiency?

Mutation in receptor for growth hormone releasing hormone; genetic syndromes like Prader-Willi syndrome and Turner's syndrome

What are some acquired causes of growth hormone deficiency?

brain trauma, infections, radiation therapy, and pituitary tumors

What are the symptoms of growth hormone deficiency in children?

Low blood glucose, severe hypoglycemia, short stature, dwarfism, and delayed bone age

What are the symptoms of growth hormone deficiency in adults?

Weakened muscles, lower bone density, fractures, poor memory, and social withdrawal

How is growth hormone deficiency typically diagnosed?

Measuring growth hormone in the blood after giving a person a stimulatory agent (epinephrine or insulin) and measure Insulin-Like Growth Factor levels. In children, X-rays of the hand to reveal delayed bone age.

How is growth hormone deficiency typically treated?

Growth hormone therapy, involving regular injections of recombinant human growth hormone.

What are the primary functions of growth hormone?

Stimulation of growth of all tissues (especially muscle and bone), cell reproduction, regeneration, promotes gluconeogenesis, and protein and fat breakdown.

How does growth hormone deficiency present differently in children versus adults?

In children, it manifests as a failure to grow and has delayed puberty. In adults, it manifests more generalized symptoms.

Dwarfism is a consequence of deficient GH where…

In children

Fatigue decreased muscle mass, and poor quality of life is a consequence of deficient GH where…

In adults

What medical intervention is ofter used as 'first line' of response in managing Growth Hormone deficiencies?

Surgery using Transsphenoidal surgery as the treatment of choice

Name other medical interventions that may be used to treat GH deficiencies/ remove pituary tumors

Medications using Somatostatin analogs, GH receptor antagonists and Dopamine Agonists-- as well as Radiation Therapy

Name some physiological states that may increase GH levels in the body

During sleep, After Excercise, During Fasting or Hypoglycemia, During Puberty, In Response to Stress, and After high protein meals

WHat stimulators are driven by the Hypothalamus that help promote the secretion of GH?

GHRH (Growth Hormone-Releasing Hormone) -> Stimulates GH release & Somatostatin (GHIH) -> Inhibits GH release

What other stimulators- besides the hypothalamus help drive GH (Growth Hormone) increases?

Ghrelin (from the stomach during fasting), Low blood glucose, High amino acid levels (arginine), & Low IGF-1 (Insulin-like Growth Factor 1)

GH increases to primarily…

Stimulate growth and cell division, Mobilize energy stores, Preserve blood glucose during fasting, & Support tissue repair and muscle recovery after stress or exercise