Module 4: Endocrinology

What is the primary function of the endocrine system?

The endocrine system is a hormone-based control system.

How do hormones achieve specificity in their actions?

Specificity comes from receptor expression on target cells.

What are the types of cell communication classified by distance?

Local (juxtacrine, autocrine, paracrine) and long-distance (endocrine, nervous system, neuroendocrine).

What are the core concepts in cell signaling?

1. Synthesis & release of messenger; 2. Transport; 3. Binding to receptor; 4. Signal transduction; 5. Cellular response; 6. Termination of information transfer.

What are the chemical classes of messengers involved in cell signaling?

Peptides, steroids, amines, lipids, DNA, RNA, and metabolites.

How are peptide hormones stored and released?

They are stored in vesicles and released by exocytosis.

What is meant by 'sensitivity of target cells'?

It depends on the number of receptors, receptor affinity, and downstream signaling capacity.

Name a key factor that influences hormone levels.

Net secretion, activation, binding to plasma proteins, and inactivation & excretion.

What happens during hormone insensitivity?

There is a reduced physiological response despite normal or elevated hormone levels.

What does PRL stand for and what is its primary function?

Prolactin; it plays a crucial role in lactation and mammary gland development.

What is the primary way to regulate prolactin secretion?

Prolactin secretion is primarily inhibited by dopamine.

Describe the feedback regulation mechanism for prolactin.

Short-loop negative feedback: PRL increases dopamine production, which then decreases PRL levels.

What are the two major postnatal growth spurts?

Infancy (birth to 24-36 months) and puberty.

What are the main actions of growth hormone (GH)?

GH promotes growth by increasing cell number and size, bone length, and has metabolic functions in muscle, liver, and adipose tissue.

What is the mechanism of action for growth hormone receptors?

GH receptors activate the JAK-STAT signaling pathway.

What are the disorders associated with abnormal growth hormone levels?

GH deficiency can lead to pituitary dwarfism, while excess GH can result in gigantism or acromegaly.

What roles does IGF-1 play in the body?

IGF-1 promotes hypertrophy, hyperplasia, and cell survival.