Hormonal Control of Growth & Puberty Part I

This set of vocabulary flashcards covers the hormonal control of growth, including Growth Hormone (GH) mechanisms, thyroid function, and calcium homeostasis as described in the lecture notes.

Growth

A process requiring the net synthesis of proteins, the lengthening of long bones, and an increase in the number and size of cells comprising soft tissue.

Somatotrophs

Cells located in the anterior pituitary that produce and release Growth Hormone (GH) periodically throughout the day.

Anabolic Hormone

A type of hormone, such as Growth Hormone, that promotes building processes including increased muscle mass and long bone growth.

Growth Hormone Releasing Hormone (GHRH)

A hypothalamic hormone that stimulates the release of Growth Hormone (GH) from the anterior pituitary.

Growth Hormone Inhibiting Hormone (GHIH)

Also known as somatostatin, this hypothalamic hormone inhibits the release of Growth Hormone (GH).

Insulin-like growth factor-1 (IGF-1)

Also known as somatomedins, these are produced by the liver in response to GH stimulation and mediate most of the long-term, growth-promoting actions of GH.

Direct Actions of GH

Short-term metabolic effects including increased blood fatty acid levels via lipolysis and increased blood glucose levels by inhibiting glucose uptake in skeletal muscle and stimulating gluconeogenesis in the liver.

Indirect Actions of GH

Long-term growth-promoting effects mediated by IGF-1, including protein synthesis, cell division, and the lengthening and thickening of bones.

Hyperplasia

An increase in cell number stimulated by cell division and the prevention of apoptosis.

Hypertrophy

An increase in cell size promoted by protein synthesis and the inhibition of protein degradation.

Epiphyseal plate

The cartilaginous area of long bones where GH stimulates proliferation to promote bone lengthening.

Cortisol

A hormone released from the adrenals during stress that is catabolic and inhibits growth.

Diurnal rhythm of GH

The pattern where GH levels remain low and constant during the day but increase sharply (up to 5 times) after the onset of deep sleep.

Insulin

A hormone produced by eta-cells of the pancreas that stimulates storage of glucose and fats, and promotes protein synthesis.

Triiodothyroxine ($T_3$)

A physiologically active thyroid hormone consisting of an amino acid core bound to 3 iodine atoms, possessing greater activity than $T_4$.

Thyroxine ($T_4$)

A thyroid hormone bound to 4 iodine atoms that is commonly converted to $T_3$ in target tissues.

Basal metabolic rate

The amount of energy required by the body at rest, which is regulated by thyroid hormones through ATP consumption and gluconeogenesis.

Parathyroid Hormone (PTH)

A hormone that maintains calcium homeostasis by increasing plasma $Ca^{2+}$ through bone release and renal reabsorption.

Calcitonin

A hormone produced by thyroid C cells that decreases plasma $Ca^{2+}$ levels by promoting calcium deposition in bone and excretion by the kidneys.

Testosterone

An anabolic reproductive hormone that stimulates bone growth in length, increases muscle mass, and increases weight.

Estrogen

A reproductive hormone that is not involved in growth stimulation but causes growth plates to close, stopping growth in length.

Normal blood calcium levels

The homeostatic range for calcium in the blood, defined as $8.5-11\,mg/dL$.