Endocrinology answers PDF

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Diana Sofia Ramirez Villamil C12205001 Thyroid Troubles: A Case Study in Negative Feedback Regulation 1. Diagram the hypothalamic-pituitary-thyroid axis. Make sure to include the feedback loops and spell out the hormone names.

2. What is the physiological role of thyroid hormones? Does T3 or T4 play a larger role on the target tissues? Explain. The thyroid gland controls the body metabolism, protein synthesis, and a body’s responsiveness to other hormones. The principal hormones are triiodothyronine known as

T3 and thyroxine known as T4. They both regulate the body’s temperature, metabolism, and heart rate by binding to proteins in the body. 3. Describe hyperthyroidism and hypothyroidism. List at least three symptoms of each. - Hyperthyroidism can mimic other health problems, this occurs when the thyroid gland produces too much of the hormone thyroxine. It accelerate the body’s metabolism causing unintentional weight loss and a rapid or irregular heartbeat. Some symptoms are tachycardia, irregular heartbeat (arrhythmia), nervousness, anxiety and irritability. - Hypothyroidism is the opposite of hyperthyroidism. The thyroid does not produce enough of certain crucial hormones some symptoms are fatigue, sensitivity to cold, constipation, weight gain, muscle weakness. 4. What is a goiter? Goiter is an abnormal enlargement of the thyroid gland. It is painless however it can cause a cough and make it difficult for a person to swallow or breath. 5. Please fill out the chart below. Record whether the hormone levels are expected to be high, low, or either. For antibody/immunoglobulins and goiter, answer yes, no, or possible. (The antibodies and immunoglobulins in question are those specific to the thyroid disorder.)

Primary hypothyroidis m (Iodine deficiency)

Grave’s Hashimoto’ Disease s Disease

TRHsecreting tumor

TSH secreting tumor

TRH TSH suppressing suppressing tumor tumor

TRH levels

High

Low

High

High

Normal to Low

Low

Normal to low

TSH level

High

Low

High

High

High

Low

Low

T3 and T4 levels

T3 Normal T4Low

High

Low

Normal

Normal

Normal

Normal

Antibodies or immunoglobulin s present?

No

Yes

Yes

No

No

No

No

Goiter present?

No

Yes

Yes

No

No

No

No

Is a patient hyper-or hypothyroid?

Hypothyroid

Hyper Thyroi d

Hypothroid

Hypothyroi d

Hypothyroi d

Hyperthroi d

Hyperthroi d

6. Use the chart below to record whether the hormone levels are expected to be high, low, or either. For antibody/ immunoglobulin and goiter, answer yes, no, or possible.

Hypothyroidism

Hyperthyroidism

TSH levels

High

Low

T3 and T4 levels

Low

High

Antibodies or Immunoglobulins?

No (Exception-Antibodies in Hashimoto’s disease)

No(Exception- antibodies in Grave’s disease)

Goiter present?

No (Exception -Hashimoto’s disease)

No (Exception-Grave’s disease)

7. If you gave a person with primary hypothyroidism (iodine deficiency) an injection of TSH would T3 and T4 levels increase? Why or why not? When a person is diagnosed with hypothyroidism the body does not produce enough T3 and T4 hormones. The injection of TSH (thyroid stimulating hormone) is used to diagnose

patients who have had thyroid cancer and need thyroid surgery. The TSH injection stimulates the production thyroxine T4 and triiodothyronine T3. 8. Some patients with HPT axis problems develop a goiter. Describe two different scenarios/conditions in which a goiter would be present and explain physiologically why/how the goiter occurs within each scenario/condition. Make sure to include axis feedback in your answer. Goiter is the enlargement of the thyroid gland. The thyroid gland is influenced by hormones produced by two other glands the pituitary gland which produces TSH (thyroid stimulating hormone) and the hypothalamus which produces TRH Thyrotropin releasing hormone. When the thyroid hormones are less in the blood the brain send a signal to the pituitary gland to release more TS. This stimulates the thyroid gland to produce T3 and T4. Goiter occurs when there is a deficiency in iodine. There is an increase in TSH to uptake of iodine by the thyroid gland and increase the production of the thyroid hormone. When there is diet with low iodine there is insufficient thyroid hormone produced so, hypothalamic TRH acts on pituitary to release TSH in large amounts. The pituitary responds and TSH is increased. This helps the thyroid to capture most of the iodine present to it from food and water. Whereas, THS also causes growth of thyroid calls which leads to goiter. In the case of the autoimmune disorder of the thyroid gland hypothyroidism arises due to improper production of TH by the thyroid gland. 9. Are any of Angela’s values outside the normal range? If so, which ones, and are they high or low? Angela's Serum thyroxine(T4), thyrotropin(TSH), and Serum iodothyronine(T3) test values are outside the normal range. All the three test values are low. (compare the result values with normal values given in the table).

10. Is Angela’s thyroid axis functioning properly? If not, does she have symptoms consistent with hypothyroidism or hyperthyroidism? No, Angela's thyroid axis is not functioning properly because the values of the thyroid profileTSH, T3, and T4 all are lower than the normal values. She has symptoms consistent with hypothyroidism. Notes  In common cases of hypothyroidism, T4 is low but the TSH is high.  T4 is the main thyroid hormone.  To check for the functioning of thyroid gland blood levels of T4 and TSH should be measured.  But here in Angela's case both T4 and TSH are low. This is the rarest case of hypothyroidism which may be due to pituitary failure.  Commonly hypothyroidism involves high TSH and low T3 and low T4.

  

Low values of T3 also indicate hypothyroidism. Low levels of T3 also indicate that a person has a long-term illness because T3 levels generally decrease when a person is sick. Doctors do not routinely advise the T3 test as a thyroid test. They advise it along with the T4 and TSH test to get a complete picture of how the thyroid gland is working.

11. Dr. Siddiqui asks you what you think is wrong with Angela. What is your diagnosis? (Note: do not simply say hyper- or hypothyroidism; that portion of the question was already answered above.) In this cases Angela is found to be gaining weight and is constantly tired and suffering from fatigue. After the thyroid test, it is most likely clear that she is suffering from hypothyroidism which is when one starts gaining weight due to hormonal issues. Hashimoto is the condition in her case which is basically an auto-immune disease and causes hypothyroidism. The disorder produces the antibodies which are against the thyroid gland causing inflammation and hence reduces the production of thyroid hormones.In such case the body is not able to produce enough thyroid hormone and hence the regulation and metabolism of the body is interrupted. The thyroid hormone is responsible for providing energy for functioning of all the organs and helps in controlling heart beat and also the digestive system. The function of the body tends to reduce without presence of enough thyroid hormone. This is something that is common with age. Some of the common symptoms associated with it is fatigue, constipation, feeling cold, weight gain, muscle weakness, decreased sweating, slow heart beat, pain in the joints etc. According to the result it is found that the serum T3 hormone is present in less quantity as compared to normal range that is required for proper functioning. The result shows that she has 57ng/dl of the T3 hormone but the normal range is between 80 – 180 ng/dl which clearly shows that she is suffering from hypothyroidism. The results clearly show that she has low level of T3 and T4 thyroid hormones.

12. Angela does not have a goiter at the moment. If her condition continues unchecked will she develop one? Why or why not? Make sure you include Angela’s blood work results to back up your response. If her condition is left unchecked she might not develop goiter because she is suffering from hypothyroidism where thyroid gland is not able to produce enough T3 and T4 hormones. The primary cause of goiter is deficiency of iodine but also due to production of excess thyroid hormones, it might lead to development of goiter. Since she is suffering from hypothyroidism and not hyperthyroidism, she is less likely to suffer from goiter.

13. Knowing what you do about the HPT axis, what hormonal information would you need to determine if the hormone-suppressing tumor is in the hypothalamus or anterior pituitary? Why is it near impossible to get this information? Regulation of metabolism is done with the help of the HPT axis. HPT refers to the hypothalamic-pituitary-thyroid axis also, HPT is part of the neuroendocrine system. This system depends upon the functioning of the hypothalamus, thyroid and pituitary glands. The abnormal growth and unregulated proliferation of cells result in tumor formation. It is given in the question that the tumor to be diagnosed is “hormone-suppressing tumor” so the doctor should prescribe blood tests to test the presence of hormones produced by hypothalamus or anterior pituitary (as the tumor suppresses the hormone production by the glands thus, the concentration of the hormones would be less than the normal range). In case of tumor formation or stress, HPA has evolved several mechanisms to control the activation of HPA axis. Hormones produced by the hypothalamus: a) Anti-diuretic hormone and oxytocin- These hormones are sent to the posterior lobe (present in the pituitary gland) from there it gets released into the bloodstream. Antidiuretic plays its role in the reabsorption of water in the kidneys while oxytocin helps in uterus contraction during childbirth. b) Hormones like thyrotropin-releasing hormone (TRH), corticotrophin-releasing hormone (CRH), somatostatin, dopamine, growth hormone-releasing hormone and gonadotrophinreleasing hormone (GRH). Hypothalamic hormone function could be disrupted by the presence of brain tumors as the tumor mentioned in the question is hormone suppressing in nature, therefore, the levels of all the above hormone will decrease then the normal range. The blood test indicating a low level of these hormones can suggest a hypothalamic tumor. Hormones synthesized by the anterior pituitary: Majorly six hormones are secreted by the anterior pituitary gland, located in the brain. These hormones include- TSH (thyroid-stimulating hormone), GH (growth hormone), ACTH (adrenocorticotropic hormone), PRL (prolactin), LH (luteinizing hormone), and FSH (follicle-stimulating hormone). Abnormality such as tumor formation (that suppresses the synthesis of these hormones) would result in the low levels of these hormones in the bloodstream. This would be indicated in the blood reports suggesting the presence of a tumor in the anterior region of the pituitary. Blood test/Hormonal testing: The exact location and tumor size cannot be precisely determined by blood tests. Imaging techniques such as CT-Scan (computed tomography) and MRI (magnetic resonance imaging) are also required to decipher the complete information about the tumor. A blood test would require various enzymatic assays in order to test the concentration (levels) of each hormone. To get a complete range of all the hormones is not a cost-effective method of tumor detection also collection of this information would require a number of antibodies and other reagents which might not be available. Hence, a collection of this data is quite impossible and unmanageable.

14. Dr. Siddiqui injects Angela with a dose of TRH and draws a blood sample to measure TSH and thyroid hor- mone levels. What results would you expect if the tumor is in the hypothalamus? The anterior pituitary? Use the table below to organize your answers (state high or low) and then explain your rationale for your answer below.

An increase in the serum TSH level following TRH administration means that the cause of the hypothyroidism is in the hypothalamus. Reason: When the hypothalamus is not producing TRH, TSH level will be very low and as TRH is given exogenously, TSH levels increase. Case - 2: If there is very slight increase in serum TSH level or absent of increase in serum TSH level following TRH administration, then the cause of the hypothyroidism is in the anterior pituitary gland. Reason: When the pituitary is not secreting TSH, even when TRH is given exogenously TSH levels do not rise as the pituitary gland is diseased....