Endocrine System & Disorders; Hormones & Feedback Loops.

Endocrine System: Hormones in Action, Endocrine Disorders, and Feedback Loops

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Part 1 - Hormones in action

Part 1 – Hormones in action

1. [3 marks] Hormones are classified as water-soluble or fat-soluble. Fat-soluble hormones directly pass through the phospholipid membrane. Water-soluble hormones require a secondary messenger. Provide three water-soluble hormones and three fat-soluble hormones in the appropriate container. An example of each one has been provided.

2. [3 marks] Answer the following True/False questions regarding steroid and peptide hormones by highlighting your answer.

a. Peptide hormones are lipid-soluble. [True / False]

b. Steroid hormones require a secondary messenger to stimulate protein synthesis in the target cells. [True / False]

c. Both steroid and peptide hormones bind to receptors like a lock-and-key. [True/False]

3. [9 marks] Complete the table below by providing the full name of the hormones, their functions and target organs.

Gland	Hormone Produced	Target Organ	Hormone Function
Anterior Pituitary	Luteinizing hormone (LH)		Testosterone production in males
Posterior Pituitary		Kidney
Adrenal Medulla	Epinephrine	Most body cells
Adrenal Cortex			Increases blood volume
Pancreas	Glucagon	Liver, Muscles, Adipose Tissue	Raises blood sugar level
Ovary		Uterus
Testes		Reproductive organs	Stimulates growth in reproductive organs

4. [4 marks] The glands listed in the table above are endocrine glands. The pancreas, however is both an endocrine and an exocrine gland.

You can navigate and zoom using the tools on the bottom of the page. There is also some helpful information provided on the right side of the page. Use this, in addition to the information in your content module, to answer the following questions.

a. State one difference between endocrine and exocrine glands.

b. The exocrine portion of the pancreas secretes its products directly into the blood. [True / False]

c. The majority of the pancreas is made up of endocrine cells. [True / False]

d. Islands of “lightly stained” endocrine cells exist within the “darkly stained” exocrine cells. [True / False ]

Part 2 – Endocrine Disorders

5. You are a freshly minted endocrinologist (a physician who has specialized in disorders related to the endocrine system). You received the following lab test results on several patients summarized in the chart below. Answer the questions that follow to assure that you are ready for the job.

Disorder	Symptoms	Lab Test Results
Acromegaly	Enlarged hands and feet, excessive sweating, fatigue, muscle weakness, pain, limited joint mobility	Elevated levels of insulin-like growth factor I
Addison's Disease	Fatigue, increased pigment in the skin, weight loss, muscle weakness	Low sodium, high potassium, high ACTH, low cortisol in the blood
Cushing's Syndrome	Backache, anxiety, muscle weakness, extra fat deposits on the back of the neck and upper back (aka "buffalo hump"), females may experience irregular menstrual cycle	High levels of cortisol in the blood
Diabetes Insipidus	Frequent urination, excessive thirst	Normal blood glucose level, no glucose in the urine, low ADH level in the blood
Hyperparathyroidism	Excessive thirst, weak or broken bones, fatigue, nausea	High calcium and parathyroid hormone levels in the blood
Hyperthyroidism	Elevated body temp, extreme sweating, nervousness, rapid heart rate, weight loss, irregular menstrual cycle in females	High thyroxine and low TSH in the blood
Hypothyroidism	Fatigue, muscle weakness, depression, weight gain, low body temperature, intolerant of cold	Low thyroxine and high TSH in the blood
Polycystic Ovarian Syndrome (PCOS)	Acne, unwanted hair growth, weight gain, fatigue, infertility, mood changes, sleep problems	Elevated levels of testosterone and LH, low levels of FSH in blood

a. [1 mark] What type of sample was used for all the lab tests? [urine / blood]

b. [1 mark] Why is the sample type you chose in 6a the preferred sample for lab tests in diagnosing endocrine disorders?

c. [1 mark] Hyperthyroidism is a condition caused by high levels of thyroxine (T4) released into the blood from the thyroid gland. Name one other hormone produced by the thyroid gland.

6. A 28-year-old woman has complained of menstrual irregularities and infertility despite actively trying to get pregnant for 14 months. She also mentioned that she has to wax her face a lot of hair growth that doesn’t align with her gender identity.

a. [1 mark] Which of the disorders listed in the table is this patient likely to have?

b. [2 marks] Once you identify the disorder, which specific hormone in the associated lab test results is likely responsibly for the unwanted hair growth? Provide a brief explanation.

Part 3 – Feedback Loops

The endocrine system plays an important role in homeostasis because hormones regulate the activity of body cells. The release of hormones into the blood is controlled by a stimulus. For example, the stimulus either causes an increase or a decrease in the amount of hormone secreted. A typical example is the homeostasis of blood sugar, which is maintained by the pancreatic hormones, insulin and glucagon. An effective way of summarizing the mechanisms by which hormones maintain homeostasis is using a feedback loop. For example, the feedback loop for blood sugar looks like this:

feedback loop for blood sugar