Week 34

Pharmacoloy recap

Welcome to our last session of pharmacology. Before we get into this session, let’s start with a quick two-question quiz before turning our focus to drug interactions and adverse effects.

Interaction mechanisms

In pharmacology, interaction mechanisms refer to the interactions between drugs as well as interactions between drugs and other compounds (such as food, supplements, or environmental substances). These interactions can affect the pharmacokinetics and pharmacodynamics of the substances involved.

As a pharmacy technician, it is important that you understand interaction mechanisms to ensure patient safety, prevent medication errors, educate patients about medication use and risks, and collaborate effectively with the healthcare team to promote safe and effective patient care.

This week, we will explore and cover the following drug interactions:

1. Drugs with other drugs
2. Drugs with other compounds
3. Drugs with diseases
4. Drugs with herbal/ natural remedies.

Interaction of drugs with other drugs (drug-drug interaction)

The interaction of drugs with other drugs presents various situations where the use of one medication may be contraindicated due to its interaction with another drug.

Can you recall instances where the administration of one drug is not recommended if a patient is already prescribed another medication?

Do you know the reasons behind these recommendations? You may recall examples from your previous learning or from the pharmacy workplace.

Examples

Read the following webpage from the New Zealand Formulary (NZF) on Drug Interaction for an overview of drug-to-drug interactions and some examples: Drug Interactions.

Types of drug-drug interactions

Let’s now look at the different types of drug-drug interactions:

Complexing

This is where one medication forms a chemical complex (they stick together) with another drug to form an insoluble salt that cannot be absorbed through the intestine. Therefore, the complex passes through the GI system and is excreted without doing its job.

Drugs that change the acidity of the stomach

Drugs that change the acidity of the stomach can affect the ability of a drug to dissolve in the stomach.

Motility

Motility refers to the movement of substances in the gastrointestinal tract. When one drug alters gut motility, it can affect how another drug is absorbed. This means drugs may move more rapidly or slowly through the gut, which can impact their absorption.

Sometimes, this interaction is used deliberately, as in the combination of paracetamol and metoclopramide, where the absorption of paracetamol is aided by an increase in gut motility.

Clearance

Clearance refers to the interaction where one drug affects the elimination or clearance of another drug from the body. This can occur through various routes, such as renal clearance (excretion via the kidneys), hepatic clearance (metabolism by the liver), or other metabolic pathways. When one drug alters the clearance of another, it can impact the concentration of the affected drug in the bloodstream.

Example

• Amiodarone (antiarrhythmic) stabilises the heart's electrical activity and restores and maintains a normal heart rhythm.
• Digoxin (cardiac glycoside) is used to increase the strength and efficiency of the heart muscle contractions.

Amiodarone decreases the renal clearance of digoxin, causing high digoxin levels in the body.

Drugs that act on the same site

When both drugs act at the same site, the following effects can occur:

1. Additive effects: A greater overall effect than if each drug were administered alone. 
2. Reduced effects: The drugs may interfere with each other's action, leading to diminished therapeutic responses. 
3. Opposing effects: The drugs may have opposing actions at the receptor site, leading to conflicting pharmacological effects.

Drugs that act on different sites

When both drugs given in combination act on different sites, they can either:

1. Potentiate (increase clinical effect) or 
2. Antagonise (decrease clinical effect) their pharmacological effects. 

In relation to enzymes, this means that there can be an enzyme induction or enzyme inhibition. 

Enzyme induction

A drug can cause the action of enzymes to increase, resulting in an increased metabolism of another drug that is metabolised using the same enzyme pathway. 

On the flip side…

Enzyme inhibition

A drug inhibits the action of an enzyme, resulting in decreased metabolism of another drug. 

Interactions of drugs with other compounds (drug interaction)

Drugs may interact with other non-drug compounds, which can affect the absorption, distribution, metabolism, and excretion of drugs in the body, altering their therapeutic effects. We will explore the interactions of drugs and the following compounds: 

1. Smoking
2. Caffeine
3. Grapefruit juice
4. Vitamin K
5. Alcohol
6. Tyramine-containing foods.

Drugs and smoking

Tobacco smoke contains compounds that can induce liver enzyme activity (increase the rate), particularly cytochrome P450 (CYP) enzymes. This induction can cause drugs processed by these enzymes to be metabolised more quickly. As a result, smokers may require higher doses of medications metabolised by these enzymes to achieve the same therapeutic effect as non-smokers.

On the other hand, when a smoker quits smoking, the induction of liver enzymes decreases, and drug metabolism returns to normal. Therefore, lower drug doses may be necessary to avoid potential overdose or adverse effects in former smokers.

Drugs and caffeine

Caffeine is found mainly in coffee, tea, and energy drinks. Most interactions with caffeine result from competitive inhibition. This means that the caffeine and the other drug can compete to be metabolised by the same enzyme. The ‘winner’ will be metabolised preferentially, resulting in higher levels in the body than the ‘loser’.

Examples

Examples of commonly used drugs that result in a clinically significant increase in caffeine levels are:

• Ciprofloxacin
• Diltiazem
• Fluconazole
• Norfloxacin
• Olanzapine
• Terbinafine
• Verapamil.

Patients starting these medicines may notice side effects from the caffeine.

Grapefruit juice

Grapefruit juice inhibits the enzyme cytochrome P450 3A4 in the gut wall. This means that any drug that is usually metabolised in the gut wall by this enzyme will not be broken down as much as it should be, and blood levels of the drug will be higher.

This interaction cannot be managed by just separating the doses, as the effect on the enzyme lasts several days after the grapefruit juice is stopped.

Examples

Examples of drugs affected by grapefruit juice are: 

• Benzodiazepines 
• Buspirone 
• Carbamazepine 
• Oestrogens (COCs)
• Statins 
• Tacrolimus.

Note: The interaction happens with grapefruit and its juice. There is a chance that it also may happen with marmalade, so this is also contra-indicated.

Vitamin K

Foods containing vitamin K can interact with certain medications, especially anticoagulants like warfarin. Warfarin functions by interfering with the action of vitamin K, which is essential for blood clotting.

Consequently, consuming vitamin K-rich foods can counteract the effects of warfarin, potentially reducing its effectiveness in preventing blood clots. Therefore, individuals taking warfarin should be mindful of their intake of vitamin K-containing foods to maintain the medication's efficacy.

Examples

Foods that are high in vitamin K include:

• Leafy green vegetables such as kale and spinach
• Brussels sprouts
• Parsley
• Lettuce
• Cabbage
• Asparagus
• Green beans.

Alcohol

Alcohol is primarily metabolised in the liver by enzymes such as alcohol dehydrogenase, acetaldehyde dehydrogenase, and microsomal enzymes in the liver, such as cytochrome P450 enzymes.

Alcohol can amplify or diminish the effects of certain drugs, leading to unpredictable outcomes or adverse reactions.

Example

Alcohol can intensify the sedative effects of some medications, leading to increased drowsiness or impaired coordination. Conversely, alcohol can also interfere with the metabolism of certain medications, affecting their absorption, distribution, or elimination from the body. This can result in altered drug levels in the bloodstream, potentially reducing the medication's effectiveness or increasing the risk of side effects.

Tyramine-containing foods

Tyramine is an amino acid that helps to regulate blood pressure. It occurs naturally in the body and can also be found in some foods.

Tyramine-rich foods can interact with certain medications, particularly monoamine oxidase inhibitors (MAOIs). MAOIs are a class of drugs prescribed for the treatment of depression. MAOIs inhibit the breakdown of tyramine in the body, leading to an accumulation of tyramine levels. This can result in a sudden increase in blood pressure, known as a hypertensive crisis, which can be dangerous. Therefore, individuals taking MAOIs should avoid or limit consumption of tyramine-rich foods to prevent adverse reactions.

Here's a quick challenge for you. What foods do you think are high in tyramine? Note down at least three examples and then expand the following label to check your answer.

Interactions of drugs with diseases (drug-disease interaction)

Some drugs can interact with specific diseases or disorders, making the diseases or disorders worse. In this week's self-directed learning activity, you will see examples of these.

Interactions of drugs with herbal/ natural remedies

There are some significant interactions between drugs and natural remedies. Always check with your pharmacist if a customer who is taking a prescribed medicine wishes to buy a natural remedy. 

Example

St John’s Wort (used to treat depression naturally) interacts with many medicines. It is an enzyme inducer, so it can increase the metabolism of some medicines, e.g. warfarin, digoxin and oestrogen. It also inhibits the reuptake of serotonin. If given with prescribed meds that also increase serotonin levels, serotonin syndrome may result. This is a serious problem that can be fatal. 

Adverse effects

An adverse drug reaction is any undesirable effect of a drug that is not expected as part of a therapeutic effect. They are classified into two groups: A and B.

Type A reactions

• These are the most common. They are predictable because they are due to the normal actions of the drug. 
• They may result from incorrect doses, decreased elimination, or increased sensitivity of organs to the drug.
  • Decreased elimination results from either reduced metabolism in the liver (liver damage) or reduced clearance by the kidneys (renal damage).
  • Increased sensitivity to drugs may result for varying reasons – e.g. in a patient with potassium deficiency, the heart becomes more sensitive to the effects of digoxin, resulting in digoxin toxicity. 

Type B reactions

These are unexpected reactions that are not dose-related. Sometimes, neither the reason nor the mechanism for the reactions can be explained.

There are several factors involved in this type of reaction, including:

• Genetic factors: These factors may make a drug act in an abnormal manner.
  • For example, some people of African, Middle Eastern and South Asian descent are deficient in the enzyme glucose-6-phosphate dehydrogenase (G6PD). If these people take ciprofloxacin, their red blood cells break down, resulting in pernicious anaemia.

• Host factors: These are individual patient characteristics or conditions that can influence how a person responds to a medication. These factors may include age, gender, genetics, underlying health conditions, organ function, and concurrent use of other medications or substances.
  • For example, a patient with HIV is more likely to have unexpected reactions to anti-infective drugs such as co-trimoxazole.
  • Women are at greater risk of developing adverse drug reactions than men due to differences in pharmacokinetic, immunological, and hormonal factors. 
• Allergic reactions: These occur after initial exposure to a drug. This exposure produces antibodies to the drug, which means that the patient suffers an allergic reaction the next time the drug is administered. Subsequent exposures elicit more severe reactions, so once it is discovered that a patient is allergic to a drug (e.g. penicillin), it becomes contra-indicated.

Patient Counselling

As a pharmacy technician, you will use your understanding of anatomy and physiology to advise patients on medication use for managing health conditions. It's crucial that you effectively communicate this information to patients and their families in a clear and understandable manner.

You must be able to provide correct and accurate information about the following:

• Names of prescribed medicine - this may include the generic and trade names.
• What each medicine is used to treat - this may include mechanisms of action as appropriate.
• The dose, frequency and instructions for administration.
• Any cautionary and advisory labels that apply.
• Storage instructions.
• Side effects and anything else to be aware of as appropriate.

Mahi pai! Excellent work! We've reached the conclusion of our pharmacology journey and wrapped up the Patient Care 2 module. As we transition into further learning sessions and start new modules, we encourage you to revisit any section of the online content to reinforce and enhance your understanding. Keep up the great work, kia mau ki te mahi nui!

Kia ora, in this session, we explore the immune system and medicines for the treatment of immune disorders as well as malignant diseases. There is a lot of content to cover this week, so plan your time well, divide your learning into chunks and take regular breaks to stand up, stretch, and move around to prevent stiffness and improve circulation.

Remember to use your learning strategies, such as taking notes, summarising key points in your own words and reaching out for help or clarification if needed. You can tackle the workload efficiently and confidently with effective time management and self-care strategies. Kia kaha rā! You’ve got this!

Immune system recap

We have discussed the immune system previously when looking at the Human Defence System in Introduction to Patient Care. That was quite a while ago! Do the phrases “specific” and “non-specific defence” ring any bells? Let's revisit and reinforce your understanding of this system, as the immune system concepts we have discussed are building blocks for the content we will cover this week.

The immune system

The immune system is a complex network of cells, tissues, and organs that work together to defend the body against harmful pathogens, such as bacteria, viruses, fungi, parasites, and other foreign substances. It can be broadly categorised into two main components: innate and adaptive immune systems.

The innate (non-specific) immune system

The innate immune system does not give long-lasting immunity against a pathogen but is quick-acting. It responds in the same way to all types of pathogens and is triggered when pathogens are identified or when damaged, injured or stressed cells send out alarm signals. There are two lines of defence:

1. The first line = barriers to prevent pathogens from entering the body. This includes the skin, mucus membranes, cilia and stomach acid.
2. The second line = back up to the first line. It includes the inflammatory response, phagocytes, and interferons.

Cells of the innate immune system

This image illustrates the different cells of the innate immune system. Expand each of the following labels to read about these types. You may like to refer back to this image to visualise the cells as the content describes them.

The adaptive (specific) immune system

The adaptive immune system (third-line defence) mainly involves two types of white blood cells (lymphocytes).

1. B lymphocytes (B cells)
2. T lymphocytes (T cells)

Both lymphocytes are produced in bone marrow; however, B cells remain in bone marrow, whereas T cells travel to the thymus. There are two main types of T cells: helper T cells and killer T cells.  

There are two types of adaptive immune system responses. These are:

1. Humoral (antibody-mediated response): This response system uses B cells and antibodies to respond to pathogens. Antibodies can also activate the complement system, a group of proteins that enhance the clearance of pathogens.  
2. Cell-mediated (cytotoxic T cell response): This is where cytotoxic T cells directly target and kill infected or abnormal cells. This response is important for eliminating pathogens, such as viruses and certain bacteria, and for controlling tumour growth by destroying cancerous cells.

Cells of the adaptive system

This illustration depicts the cells of the adaptive system. As you expand each of the following labels to read about these cells, make sure to refer to this illustration to create a visual association.

You will notice that there are immune cells that participate in both innate and adaptive immune responses. These cells bridge the gap between the two systems, facilitating communication and coordination of immune responses. Later, in your SDL activities for this week, you will learn more about each of these immune systems.

Phew, as this was a lot of content to absorb, complete the following seven-question pātaitai (quiz) to check your understanding.

Lymphatic system

The lymphatic system is a system we have not discussed previously. It is part of the immune system and plays a major part in the body’s defence against infection and cancer. It is a collection of organs, ducts and tissues responsible for fighting infection and draining lymph back into the bloodstream.

Watch: The Circulatory System Part 3: The Lymphatic System (7:06 minutes)

Join our good friend, Professor Dave, as he explains what lymph is, what it has to do with the circulatory system and what the lymphatic system actually does. Feel free to take notes as you watch and then complete the short quiz that follows to summarise the difference between lymphatic vessels and lymph nodes.

Disorders of the immune system

Allergy

Allergies are an immune disorder caused by an inappropriate response of the immune system to a substance (allergen) that, in most people, causes no response. When an allergen enters the body for the first time, it is identified as foreign, triggering a response from plasma cells. These specialised B cells produce antibodies, specifically immunoglobulin E (IgE), against the allergen. These antibodies then attach to mast cells, which are tissue cells containing packets of histamine and other substances.

Upon re-exposure to the same allergen, it binds to the antibodies on the surface of mast cells, leading to their rupture and the release of inflammatory substances, including histamine. This release results in allergic symptoms. It is believed that individuals with higher levels of IgE are more prone to allergies, often described as atopic, experiencing conditions like asthma and eczema more frequently.

This image from Allergy New Zealand simply illustrates how allergies develop, using a common allergen, pollen, as an example.

If you wish to read more, check out the webpage here: What is an allergy?

Signs and symptoms

You will be familiar with the signs and symptoms of allergic reactions (such as hay fever). These include the following:

• Sneezing
• Runny or stuffy nose (rhinorrhoea or nasal congestion)
• Itchy nose
• Postnasal drip (mucus dripping down the throat from the back of the nose)
• Itchy, watery eyes (allergic conjunctivitis)
• Coughing (usually due to postnasal drip)
• Scratchy or sore throat.

Treatment

Treatment for allergic reactions typically involves the use of antihistamines, which function by inhibiting action at the H1 receptor. They work by blocking the effect of histamine, one of the chemicals released during an allergic reaction. Histamine causes dilation of blood vessels, leading to redness and swelling due to fluid leakage into the tissue. However, since histamine is not the sole chemical responsible for allergic reactions, antihistamines address most, but not all, symptoms of inflammation.

Other pharmacological treatments may include steroids and decongestants.

Anaphylaxis

Anaphylaxis is an immune system disorder. It is a severe allergic reaction that can occur rapidly after exposure to an allergen. During anaphylaxis, the immune system overreacts to an allergen, leading to widespread physiological (functional) changes in the body. These changes typically involve the release of various inflammatory mediators, particularly histamine, from immune cells such as mast cells and basophils. 

Histamine causes:

• vasodilation (widening of blood vessels)
• increased vascular permeability (leakage of fluid from blood vessels into surrounding tissues)
• smooth muscle contraction, particularly in the airways. 

Other inflammatory mediators, such as leukotrienes and prostaglandins, contribute to the systemic inflammatory response, further exacerbating symptoms. If left untreated, anaphylaxis can progress to anaphylactic shock, where a severe drop in blood pressure can lead to organ failure and death.

Treatment

Anaphylaxis is a medical emergency and is treated with adrenaline (epinephrine). 

Watch: HOW DOES ADRENALINE/ EPINEPHRINE WORK [..] (3:22 minutes)

Join Maya, a woman who lives with severe food allergies, as she explains how adrenaline/epinephrine works to treat the body when suffering from an allergic reaction.

Autoimmune disorders

These disorders are similar to allergic reactions, but instead of the allergen being a ‘foreign invader’, the immune system wrongly identifies its own tissue or organs as foreign. Autoimmune disorders occur when lymphocytes begin to produce antibodies, but the underlying cause is not well understood. There are many autoimmune disorders, but here we will discuss rheumatoid arthritis (RA).

Rheumatoid Arthritis (Mate rumatiki)

Have a look at the illustration above to review the difference between a healthy joint and rheumatoid arthritis, and then let’s recap what we know about rheumatoid arthritis:

• It is a chronic, systemic inflammatory autoimmune disorder.
• Anyone can get rheumatoid arthritis at any age, but it commonly develops between the ages of 25 and 50.
• Causes are not fully understood, but women are affected more than men, and smokers have a higher rate than non-smokers.
• It may affect many tissues and organs but mainly attacks the joints, producing inflammation of the synovial membrane that lines joints and tendon sheaths. 
• Joints become swollen, tender and warm, and stiffness limits their movement, particularly early in the morning on waking or following prolonged inactivity. 
• Joints are affected symmetrically. For example, if the left knee is affected the right knee will be also.
• With time, RA nearly always affects multiple joints, most often the small joints of the hands, feet and cervical spine, but larger joints like the shoulder and knee can also be involved. 
• Eventually, there is a loss of movement and erosion of the joint surface, causing deformity and loss of function. 
• Rheumatoid arthritis can also produce inflammation in the lungs, pericardium, pleura, and sclera, and also nodular lesions, most common in subcutaneous tissue under the skin. 
• Symptoms may come and go with no particular pattern. Some people will have flares and periods of remission.

Treatment

The pharmacological treatment for rheumatoid arthritis (RA) typically involves the use of several classes of medications aimed at reducing inflammation, relieving pain, slowing down disease progression, and improving overall joint function.

Select the (+) symbols to read about each of the following treatments:

Cancer

Cancer (malignant neoplasm) is a class of diseases in which a group of cells display uncontrolled growth, invasion (intrusion on and destruction of nearby tissue), and sometimes metastasis (spread to other locations in the body via lymph or blood). Most cancers form a tumour, but some, like leukaemia, do not.

Normal cells undergo a tightly regulated process of growth, division, and death (apoptosis) to maintain tissue homeostasis. However, cancer cells acquire mutations or genetic alterations that disrupt these regulatory mechanisms, leading to uncontrolled cell growth. Tumour suppressor genes are inactivated in cancer cells, resulting in the loss of normal functions in those cells, such as accurate DNA replication, control over the cell cycle, orientation and adhesion within tissues, and interaction with protective cells of the immune system.

Cancer can arise from any type of cell in the body and is caused by a combination of genetic, environmental, and lifestyle factors. Genetic mutations can be inherited or acquired throughout life due to exposure to carcinogens (e.g., tobacco smoke, ultraviolet radiation, certain chemicals), viral infections (e.g., human papillomavirus, hepatitis B virus), hormonal factors, immune dysfunction, and other factors.

Cell growth

Here, you can compare the effects of normal and abnormal cell growth with the abnormal cell growth resulting in a malignant tumour. 

Tumours

A tumour is an abnormal growth of cells that can develop in various tissues or organs of the body. Tumours can be classified into two main types: malignant (like the image above) and benign tumours. Let's look at malignant first.

Malignant tumours

These are also known as cancerous tumours. They are growths of abnormal cells that have the ability to invade surrounding tissues and spread to other parts of the body, a process known as metastasis. They often have irregular shapes, may grow rapidly, and can cause significant damage to nearby tissues and organs.

They are life-threatening and often require aggressive treatments such as surgery, chemotherapy, radiation therapy, or targeted therapy to prevent further spread and improve outcomes.

Examples

• Carcinomas (originating from epithelial tissues)
• Sarcomas (originating from connective tissues)
• Lymphomas (originating from lymphocytes)
• Leukaemia (originating from blood-forming cells).

Benign tumours

These are non-cancerous growths that do not spread to other parts of the body or invade surrounding tissues. They are typically well-defined and may grow slowly over time. They may cause symptoms depending on their size and location but are generally not life-threatening. They may require monitoring or surgical removal for symptom relief.

Examples

• Uterine fibroids
• Lipomas (fatty tumours)
• Moles.

Breast Cancer (Mate pukupuku ūtaetae)

Oestrogen and progesterone receptors are proteins found on the surface of breast cells. These receptors are present in healthy breast cells and help control the way breast cells grow, but in 70% of breast cancers, the receptors are over-expressed. These cancers are called hormone-sensitive or hormone receptor-positive, meaning that oestrogen and progesterone can attach to the receptors and fuel the growth of the cancer.

Breast cancer can be divided into two groups:

1. Non-invasive (in situ) - cancerous cells that remain confined within the ducts or lobules of the breast tissue and have not spread into surrounding healthy tissue. It is considered an early stage of breast cancer (pre-invasive).
2. Invasive - cancerous cells that have breached the basement membrane of ducts or lobules and have invaded surrounding healthy breast tissue. It has the potential to spread (metastasise) to nearby lymph nodes and other organs of the body via the bloodstream or lymphatic system.

Treatment

Pharmacological treatments for breast cancer include a variety of medications that target different aspects of the disease. Here, we will focus on tamoxifen.

Tamoxifen is a type of hormonal therapy used in the treatment of hormone receptor-positive breast cancer. Hormone receptor-positive breast cancer refers to a type of breast cancer in which the growth of cancer cells is driven by the presence of hormone receptors (oestrogen and progesterone) on the surface of the cancer cells. Tamoxifen works by blocking the oestrogen receptors in the cancer cells to prevent them from responding to signals from the oestrogen to grow and multiply.

Melanoma (Mate pukupuku kiri manauri)

Melanoma is a type of skin cancer originating from melanocytes, pigment-producing cells in the skin. It primarily affects the integumentary system, which includes the skin, and can occur anywhere on the body but is most commonly found in sun-exposed areas.

Melanoma occurs when melanocytes undergo malignant transformation and begin to grow uncontrollably. If left untreated, melanoma can invade deeper layers of the skin, blood vessels, and lymphatic vessels, allowing it to spread (metastasise) to other parts of the body, such as the lymph nodes, lungs, liver, brain, or bones.

Stages of melanoma

Here, you can see the five stages of melanoma, with the tumour becoming malignant as it spreads.

Signs and symptoms

Melanoma is less common than other types of skin cancer but is more aggressive and has a higher risk of metastasis. Signs and symptoms may include:

• The fast appearance of a new spot or mole on the skin.
• An existing spot, freckle or mole that changes colour, size or shape (see the ABCDE of Melanoma illustration below).
• A spot that is itchy, tender, painful or bleeds.
• A spot that is raised or shiny.

Treatment

Treatment for melanoma depends on various factors, such as the disease's stage, the tumour's location and size, and the individual's overall health.

One type of pharmacological treatment is immunotherapy. It activates or enhances the body’s immune response against cancer cells.

Example

Let’s look at the example of the drug pembrolizumab.

Pembrolizumab is typically administered intravenously in a hospital setting. It is a type of medication known as an immune checkpoint inhibitor, belonging to a class of drugs called monoclonal antibodies.

Pembrolizumab works by inhibiting PD-1 receptors found on immune cells. These receptors play a crucial role in distinguishing between normal and foreign cells. When foreign cells, such as pathogens or cancer cells, are detected, the immune system responds by initiating an attack to eliminate them. However, cancer cells can mimic normal cells to hide from immune detection. Pembrolizumab blocks PD-1 receptors, preventing cancer cells from hiding from the immune system. This action enhances the immune response, enabling the identification, attack, and elimination of cancer cells.

Papillary thyroid cancer

The thyroid lies at the front of the neck, beneath the voice box (larynx) and is shaped like a butterfly. As you can see in the illustration, it has two lobes that are separated by a thin section called the isthmus. You will remember from previous weeks of learning that the thyroid gland produces hormones that regulate metabolism and other essential functions in the body. These hormones include the following:

• Thyroxine (T4) plays a key role in regulating metabolism, growth, and development and maintaining body temperature and energy levels.
• Triiodothyronine (T3) is the biologically active form of thyroid hormone that is derived from thyroxine (T4). It is more potent than T4 and is involved in many of the same physiological processes, including metabolism, growth, and development.
• Calcitonin is a hormone produced by special cells in the thyroid gland called C cells or parafollicular cells. It helps regulate calcium levels in the body by inhibiting the breakdown of bone and promoting calcium excretion by the kidneys.

Signs and symptoms

Papillary thyroid cancer is a type of thyroid cancer. It often presents as a painless lump or nodule in the thyroid gland. While it can spread to nearby lymph nodes, papillary thyroid cancer generally has a favourable prognosis when diagnosed and treated early.

Thyroid cancers usually develop slowly without any obvious symptoms. The following signs and symptoms can be experienced, but they also occur in conditions that are not thyroid cancer:

• Painless lump or nodule in the front of the neck near the Adam's apple. 
• Trouble swallowing or breathing.
• Voice changes, e.g., hoarseness.
• Swollen glands (lymph nodes) in the neck.

Treatment

Depending on the type and stage, thyroid cancer may be treated with surgery, radioactive iodine, hormone treatment, external radiation, or chemotherapy. Some patients receive a combination of treatments.

Radioactive Iodine Therapy

This treatment uses radioactive iodine (I-131, an isotope created from iodine to emit radiation) to destroy thyroid cancer cells anywhere in the body. The intestine absorbs the I-131, which flows through the bloodstream and collects in thyroid cells. Radioactive iodine is chemically identical to nonradioactive iodine. Therefore, the thyroid gland, which takes up iodine to make thyroid hormone, cannot distinguish between the two. Thyroid cancer cells remaining in the neck and those that have spread to other parts of the body are killed when they absorb I-131. It is a targeted treatment. It will not affect other body cells as only thyroid cells pick up iodine.

Radioactive iodine therapy is typically administered orally in the form of a capsule or liquid solution. It may be administered as an outpatient or, if the dose is high, as an inpatient in isolation to protect others from exposure to radiation. After treatment, the radioactive iodine is excreted from the body through urine and sweat over time. Most radiation is gone in a few days. Within 3 weeks, only traces of radioactive iodine remain in the body.

Whakamihi! Congratulations! We've successfully concluded our study of anatomy and physiology, reaching the end of this module. Next week, we focus on selecting medicines to treat disorders of different body systems.