Endocrine System Comprehensive Review

A set of 70 Question & Answer flashcards covering key glands, hormones, mechanisms, disorders, and regulatory principles of the endocrine system.

What is the endocrine system + function?

A complex network of glands and organs that produce and secrete hormones directly into the bloodstream.

hormones act as chemical messengers, regulating metabolism, growth and development, tissue function, reproduction, sleep, and mood,

What is the primary way the endocrine system communicates with target cells?

By secreting hormones into the bloodstream that bind to specific receptors on target cells.

How do endocrine glands differ from exocrine glands?

Endocrine glands are duct-less and release hormones into extracellular fluid/blood; exocrine glands have ducts and release non-hormonal secretions onto an epithelial surface.

Give two examples of exocrine glands.

Sweat (sudoriferous) glands and sebaceous (oil) glands.

Where is the pituitary gland located?

In the sella turcica of the sphenoid bone, inferior to the hypothalamus.

Through what structure is the pituitary connected to the hypothalamus?

The infundibulum.

What are the two lobes of the pituitary and their tissue types?

Anterior lobe (adenohypophysis, glandular tissue) and posterior lobe (neurohypophysis, neural tissue).

Which hormones are produced and secreted by the anterior pituitary lobe (adenohypophysis) and what are its parts?

The anterior pituitary, also known as the adenohypophysis, is composed of glandular tissue. Its major parts include the pars distalis and pars intermedia. It synthesizes and secretes six main hormones:

• Growth Hormone (GH)

• Thyroid-Stimulating Hormone (TSH)

• Adrenocorticotropic Hormone (ACTH)

• Follicle-Stimulating Hormone (FSH)

• Luteinizing Hormone (LH)

• Prolactin (PRL)

• 
  The pars intermedia specifically secretes Melanocyte-Stimulating Hormone (MSH).

What vascular system carries hypothalamic releasing hormones to the anterior pituitary?

The hypophyseal portal system.

Which hormones are released by the posterior pituitary lobe (neurohypophysis) and what are its parts?

The posterior pituitary, also known as the neurohypophysis, is composed of neural tissue. It consists of the pars nervosa and infundibulum. It does not synthesize hormones but rather stores and releases two hormones produced by the hypothalamus:

• Antidiuretic Hormone (ADH)
• Oxytocin (OT)

What is the main renal effect of ADH?

It promotes water reabsorption in the kidneys, concentrating urine.

What disorder results from ADH deficiency?

Diabetes insipidus, characterized by polyuria and polydipsia.

List two physiological roles of oxytocin.

Uterine contractions during labor and milk ejection during breastfeeding (also social/parental bonding).

Excess growth hormone in adulthood causes which condition?

Acromegaly.

Where is the thyroid gland located?

Anterior neck, below the thyroid cartilage and above the trachea.

What proteinaceous substance fills thyroid follicles?

Colloid containing thyroglobulin.

Which two iodine-containing hormones are produced by the thyroid?

Thyroxine (T4) and triiodothyronine (T3).

What is the primary function of T3/T4?

Increase basal metabolic rate, growth, heat production, and CNS development.

Which thyroid hormone is more active in peripheral tissues?

T3.

What hormone, produced by C-cells, lowers blood calcium levels?

Calcitonin.

How does calcitonin decrease blood Ca2+?

By stimulating osteoblasts and inhibiting osteoclasts.

What hormone is antagonistic to calcitonin?

Parathyroid hormone (PTH).

What condition results from iodine deficiency in the diet?

Goiter—an enlargement of the thyroid gland.

How many parathyroid glands are usually present?

Four (two pairs).

List three actions of PTH that raise blood calcium.

Stimulates osteoclasts, increases renal Ca2+ reabsorption (while excreting phosphate), and activates vitamin D for greater intestinal absorption.

What clinical problem can hyperparathyroidism cause?

Bone demineralization and kidney stones.

Which gland secretes thymosin?

The thymus.

What is the main function of thymosin?

It promotes proliferation and maturation of T-lymphocytes.

In which life stage is the thymus largest and most active?

Childhood; it involutes after puberty.

Where are the adrenal glands located?

On top of each kidney within the renal fascia.

Name the three zones of the adrenal cortex from outer to inner.

Zona glomerulosa, zona fasciculata, and zona reticularis.

Which hormone is the principal mineralocorticoid and what is its key effect?

Aldosterone; it increases Na+ reabsorption, water retention, and K+ excretion in the kidneys.

What stimulates the release of aldosterone?

Mainly the renin-angiotensin-aldosterone system (RAAS) and high blood K+ levels.

What is the major glucocorticoid and list two of its actions.

Cortisol; raises blood glucose via gluconeogenesis and exerts anti-inflammatory/protein-lipid catabolic effects.

Weak adrenal androgens such as DHEA contribute to which features?

Pubic/axillary hair and female libido; they can convert to estrogens after menopause.

What cells make up the adrenal medulla and what do they secrete?

Chromaffin cells; they secrete epinephrine (~80%) and norepinephrine (~20%).

List three fight-or-flight responses produced by adrenal medulla catecholamines.

Increased heart rate, bronchodilation, and glycogenolysis (raising blood glucose).

What syndrome results from excess cortisol?

Cushing’s syndrome.

Adrenal cortical insufficiency is called what?

Addison’s disease.

Tumor of the adrenal medulla producing excess catecholamines is termed what?

Pheochromocytoma.

What percentage of the pancreatic mass is endocrine islets?

About 1%.

Which pancreatic islet cells secrete insulin?

Beta (β) cells.

What is the primary effect of insulin?

Lowers blood glucose by enhancing cellular uptake, glycogenesis, and lipogenesis.

Which hormone released by alpha (α) cells raises blood glucose?

Glucagon.

Define Type 1 diabetes mellitus.

Autoimmune destruction of β-cells leading to absolute insulin deficiency; insulin-dependent.

What underlies Type 2 diabetes mellitus?

Insulin resistance of target cells, often associated with obesity.

Hypoglycemia can be caused by an excess of which hormone?

Insulin.

What hormone is produced by Leydig cells of the testes and name two of its roles.

Testosterone; it develops male secondary sexual characteristics and is required for spermatogenesis.

What ovarian structure secretes progesterone after ovulation?

The corpus luteum.

Which pituitary hormones regulate ovarian follicular development and ovulation?

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

Name the stages of follicular maturation in the ovary in correct order.

Primordial, primary, secondary, Graafian (mature).

What are amino-acid derivative hormones?

Hormones synthesized from single amino acids such as tyrosine (thyroid hormones, catecholamines) or tryptophan (serotonin, melatonin).

Why do steroid and thyroid hormones have longer half-lives in blood?

Because they are mostly bound to transport proteins, creating a circulating reserve.

What is down-regulation of hormone receptors?

A decrease in receptor number in response to high hormone levels, reducing cellular sensitivity.

Which type of receptors do peptide hormones bind and what messenger system do they usually activate?

Extracellular membrane receptors that typically activate second messengers like cAMP.

What is amplification in hormone signaling?

A single hormone-receptor interaction triggers production of thousands of second messenger molecules, greatly magnifying the effect.

Which hypothalamic pathway directly controls the adrenal medulla?

Sympathetic pre-ganglionic neurons (neural control).

What anterior pituitary hormone stimulates the thyroid gland?

Thyroid-stimulating hormone (TSH).

Which hormone from the anterior pituitary promotes milk production?

Prolactin (PRL).

What pineal hormone helps regulate circadian rhythms?

Melatonin.

Which kidney hormone stimulates red blood cell production?

Erythropoietin (EPO).

The heart releases ANP and BNP to produce what effect on blood pressure?

They lower blood pressure and blood volume by promoting Na+/water loss and opposing angiotensin II.

What adipose-derived hormone signals satiety and permits GnRH secretion?

Leptin.

When two hormones produce opposite effects on the same parameter, their interaction is termed what?

Antagonistic interaction.

Name the three stages of the General Adaptation Syndrome in order.

Alarm, resistance, and exhaustion.

During the resistance phase of stress, which hormones dominate?

Glucocorticoids, especially cortisol.

Which hormones are essential for normal childhood growth alongside GH?

Thyroid hormones, insulin, PTH with calcitriol, and sex steroids.

What age-related change in endocrine function occurs in women?

Menopause—a decline in ovarian estrogen and progesterone.

What is the primary common feedback mechanism used by endocrine systems?

Negative feedback.

Give an example of a permissive hormone interaction.

Thyroid hormones permitting epinephrine to exert its full lipolytic effect (other valid examples acceptable).