The Endocrine System, Questionnaire Example

Which organs make up the endocrine system?

The endocrine system is composed of the following glands: pituitary, thyroid, parathyroids, adrenals, and pineal body. In addition the reproductive organs including the ovaries and testes and pancreas play an important role.

A recurring motif in biology are positive feedback systems and negative feedback systems. What is the difference between these? Where would we expect to see a negative system and where would we expect to see a positive system? Which system is more common?

The positive feedback system occurs when a produced biological molecule is used to feed into a system that creates more of that molecular. Meanwhile, the negative feedback system is used to shut down this production once the concentration of a particular molecule is too large. An example of positive feedback is when oxytocin stimulates and enhances labor contractions; more oxytocin is constantly produced to continue production of these contractions. An example of negative feedback is the regulation of the blood calcium level. When there is too much blood calcium, calcium will interact with receptors that shut down the calcium production process.

How are the anterior and posterior pituitary controlled? Explain, in terms of their structure, why they are different.

The hypothalamus signals to the pituitary to trigger the release of hormones. The anterior lobe produces and releases hormones, while the posterior lobe releases them into the circulation. The anterior pituitary is smaller and closely intertwined with the hypothalamus, the hormones are then passed on to the posterior pituitary, which is further from the hypothalamus.

List the hormones produced by the anterior pituitary, and their major target.

Adrenocorticotropic stimulates the adrenal glands to produce hormones, follicle-stimulating hormone works with LH to ensure the normal functioning of the ovaries and testes, growth hormone maintains a healthy body composition and for growth in children, luteinizing hormone works with FSH to ensure normal functioning of the ovaries and testes, prolactin stimulates breast milk production, and thyroid-stimulating hormone stimulates the thyroid gland to produce hormones.

List the hormones produced by the posterior pituitary and the pars intermedia, and their major target.

The hormones produced by the posterior pituitary include anti-diuretic hormone which prompts the kidneys to increase water absorption in the blood and oxytocin which is involved in a variety of processes, such as contracting the uterus during childbirth and stimulating breast milk production. The pars intermedia hormone is the melanocyte stimulating hormone, which triggers the release of melanin pigment in skin melanocytes.

What is the role of the pineal gland? What happens to it as you age?

The pineal gland releases melatonin. The number of calcium structures increase with age.

What is the role of TH in the body?

TH stimulates thyroid production.

Describe the pituitary-thyroid axis, explaining how levels of thyroid hormone are regulated.

The pituitary-thyroid axis regulates metabolism and involves interactions between the hypothalamus, the pituitary gland, and the thyroid gland. The thyroid hormone operates to detect levels of T3 and T4. If they are low, TRH is released, which stimulates the pituitary to produce TSH. The TSH, stimulates the thyroid to produce thyroid hormone until levels reflect normal levels in the blood.

A dietary iodine deficiency results in an endemic goiter. Once upon a time, this was a relatively common problem, until iodine was mandated to be added to table salt (e.g. Morton’s iodized salt). Why does a lack of iodine result in a goiter?

Goiters form when the thyroid gland produces too much thyroid hormone. Iodine provides a negative feedback signal that prevents the production of excessive hormone.

What are the roles of calcitonin and PTH?

Calcitonin reduces blood calcium and PTH acts to increase it.

What are the hormones produced by the adrenal medulla? What do they do?

Epinephrine helps the body respond to stress by increasing the heart rate and force of heart contractions. Norepinephrine contributes to vasoconstriction to maintain blood pressure.

What are the three major categories of hormones released by the adrenal cortex? What do they do?

Cortisol controls the use of fats, proteins, and carbohydrates, and suppresses inflammation. Aldosterone regulates the level of sodium and potassium in the body and helps maintain blood volume and blood pressure. Androgenic steroids are converted to estrogen and androgen.

What are the two major hormones produced in the pancreas? What do they do?

Insulin increases the storage of glucose, fatty acids and amino acids in cells and tissues. Glucagon mobilizes glucose, fatty acids and amino acids from stores into the blood.

How are hydrophilic and lipophilic hormones transported differently throughout the body?

Hydrophilic hormones can be transported in dissolved water and lipophilic hormones are transported in fats.

Classified by their chemistry; what are the four structural categories of hormones? Give one example from each category. What is each category synthesized from? Finally – there is an easy way to recognize if a hormone is a steroid hormones based on its name alone. Can you figure out what this is?

The four structural categories of hormone include peptides and proteins, steroids, amino acid derivatives, and fatty acid derivatives (eicosanoids). Peptides and proteins are synthesized from amino acids, ex. serum albumin. Steroids are derivatives of cholesterol, ex. sterol. Amino acid derivatives are modifications of amino acids, ex. epinephrine. Fatty acid derivatives are modifications of fatty acids, ex. prostaglandin. The word’s suffix is indicative of their category and the root is what it was derived from.

Contrast diabetes insipidus with diabetes mellitus. What does the word “diabetes” really mean?    

Diabetes insipidus is caused by a deficiency of the pituitary hormone vasopressin, while diabetes mellitus is an inability to use insulin. Diabetes could just mean a deficiency.

What causes adrenogenital syndrome (AGS)?

Adrenogenital syndrome is typically genetic and caused by the lack of an enzyme that produces cortisol and aldosterone. In this disease, the protein machinery that makes this enzyme is damaged.