Learning Outcomes
By the end of this section, you should be able to:
- 7.1.1 Recognize the normal function of the endocrine system.
- 7.1.2 Recognize cues of nutritional impact on the endocrine system.
- 7.1.3 Analyze cues of nutritional impact on the endocrine system.
Normal Function of the Endocrine System
The endocrine system is a network of cells, tissues, and organs that regulate and control all processes using hormones. Hormones are secretions that help regulate organ function by exerting their effects on certain cells in the organ. They coordinate biological functions like metabolism, sexual reproduction, blood pressure, body temperature, heart rate, growth, development, and sleeping. Related to nutrition, the endocrine system regulates appetite and how nutrients are used.
The hypothalamus is a region in the brain that regulates the endocrine system through its connection and coordination with the nervous system. The pituitary gland, also located in the brain, regulates other glands like the adrenal, thyroid, and testicles. These glands include the thyroid, parathyroid, adrenal, pineal, and pancreas which play critical roles in regulating calcium levels in the body, metabolism, sexual development, and blood pressure, and insulin production, respectively. Figure 7.2 shows the pituitary gland and other key parts of the endocrine system. The goal of regulating hormone levels in the blood is to reach a state of balance or homeostasis. Imbalances can lead to health problems like high blood pressure, changes in mood and behavior, and weight gain (Betts et al., 2022).
Nutrition plays a vital role in maintaining homeostasis and affecting hormone functions. Overall, a balanced diet with limited ultra-processed food, a variety of fruits and vegetables, whole grains, and lean protein sources is important for endocrine health. This diet helps individuals maintain a healthy weight and decrease the risk for hormonal imbalances. Table 7.1 lists the glands that play a key role in secreting and regulating hormones and related nutritional factors.
| Gland | Role | Related Nutritional Factors |
|---|---|---|
| Adrenal glands | Release cortisol (steroid hormone) commonly referred to as the “stress hormone” | Adequate protein intake (5–7 oz eq/day for adults) as part of a balanced diet |
| Hypothalamus | Instructs the pituitary gland when to release hormones | Diet low in ultra-processed foods which decreases inflammation |
| Ovaries | Produces sex hormones including estrogen and progesterone | Balanced diet with limited red meat and poultry |
| Pancreas | Controls the release of insulin and glucagon, which are involved in regulating blood glucose levels and affecting digestion | Limited added sugar, refined grains, overall calories |
| Pineal gland | Produces melatonin, which helps regulate sleep | Foods containing melatonin have not been found to affect pineal gland function |
| Pituitary gland | Known as the “master gland,” it influences many other endocrine glands, including the thyroid. It affects various bodily functions such as blood pressure, metabolism, and growth. | (< 2300 mg/day); diet low in ultra-processed foods which decreases inflammation |
| Testes | Produces the sex hormone testosterone | Foods or supplements containing omega-3 fatty acids |
| Thyroid | Controls metabolism, heart and digestive function, mood, and muscle and bone development | Adequate iodine intake through iodized salt, fish, shellfish, dairy, seaweed |
Alterations in Endocrine System Function
Endocrine disorders develop in one of two ways. Primary endocrine disorders result from problems with the peripheral glands, while secondary endocrine disorders result when the pituitary gland is either overstimulated or understimulated by the hypothalamus causing an alteration in the peripheral gland’s function. The result of all endocrine disorders is either hyper-functioning or hypo-functioning of the affected gland.
Alterations in Endocrine System Function – Diabetes
The most prevalent endocrine disorder is diabetes (Agency for Healthcare Research and Quality, n.d.). It is estimated that 37.3 million Americans have diabetes, with approximately 8.5 million cases (23%) undiagnosed (National Institute of Diabetes and Digestive and Kidney Diseases, 2023). Diabetes develops when the body is not able to maintain adequate blood glucose control (Sapra & Bhandari, 2023). Type 1 diabetes typically develops early in life and occurs when insulin producing cells (beta cells) are destroyed in the pancreas resulting in low to non-existent levels of insulin. Type 2 diabetes results from insulin resistance that develops gradually from obesity and aging. The insufficient amount of insulin (type 1 diabetes) and/or functionally ineffective amounts of insulin (type 2 diabetes) result in elevated blood glucose levels.
Glycemic control, which is the maintenance of optimal blood glucose levels, is essential to manage potential complications of diabetes effectively. Poorly controlled blood glucose levels lead to vascular and neurological complications including myocardial infarctions, cerebral vascular accidents, renal disease, neuropathies, and retinopathy (Sapra & Bhandari, 2023). These complications result from several different mechanisms triggered by elevated blood glucose levels that either cause buildup within vessels that impede blood flow, reduce the ability of the vessels to autoregulate, or trigger altered biochemical processes that hinder the vessel’s functionality (Brutsaert, 2022). The risk for these conditions developing is increased in clients who have co-morbid conditions.
Special Considerations
Differences in Insulin Sensitivity Among Diverse Populations
Members of US racial/ethnic minority groups have higher rates of insulin resistance than non-Hispanic White members of the population. This is most likely attributed to both genetic and lifestyle factors (Caballero, 2018).
Alterations in Endocrine System Function – Other Endocrine Disorders
Other endocrine disorders commonly seen are hypo/hyperthyroidism and adrenal disorders. Hypothyroidism results from the decreased levels of thyroid hormones T4 and T3. Accordingly, thyroid stimulating hormone (TSH) is increased, indicating that the thyroid gland is not functioning properly. It usually results from autoimmune causes, but it could also occur after radioactive iodine therapy or surgery for hyperthyroidism or goiter (Braunstein, 2022). Hyperthyroidism is caused by increased secretion of T4 and T3 caused by Graves’ disease, goiter, or thyroiditis. Adrenal insufficiency is caused by Addison’s disease or a disorder regulating the pituitary gland and results in low cortisol levels in the body (Grossman, 2022). In an effort to stimulate the adrenal glands, adrenocorticotropic hormone (ACTH) is released. Conversely, Cushing’s disease/syndrome develops when corticosteroid levels in the body are high either from taking corticosteroid medications or from overproduction by the adrenal glands.
Assessment of Nutrition and the Function of the Endocrine System
Endocrine disorders can be difficult to diagnose. Frequently these conditions develop over time, and clients present with symptoms that are non-specific. A thorough history and physical is essential.
Health History and Physical Assessment
Taking a client’s health history is the first step when assessing the client’s endocrine system. In addition to general health history questions, it is important to identify conditions for which the client may be at risk and to assess the need for genetic testing (Bickley et al., 2021). When collecting information on the client’s nutritional status for potential effects on the endocrine system, the nurse should ask about changes in appetite, thirst and fluid intake, and bowel function. It is also important to know if the client has experienced any changes in weight or energy levels.
After obtaining a thorough health history, a physical assessment should be performed to look for signs of endocrine dysfunction:
- Inspect the body, looking for abnormal hair growth, skin changes, and abnormal body proportions.
- Auscultate heart sounds for rate and rhythm as some endocrine disorders cause tachydysrhythmias. Also listen over the carotid arteries and directly over the thyroid gland for any bruits.
- Palpate the thyroid gland (Figure 7.3), adrenal glands, and testes for tenderness, size, symmetry, and shape, looking for any nodules, enlargement, or changes in texture.
- Assess weight, height, and body mass index (BMI) for any changes in body composition.
- Assess sexual development, including secondary sex characteristics, and menstrual cycles.
- Evaluate the client’s mood and behavior for any changes.
- Perform point-of-care blood glucose testing (Bickley et al., 2021).
Laboratory Tests for Endocrine Functioning
Laboratory testing for endocrine disorders includes tests measuring hormones, vitamin levels, electrolytes, and kidney function among others. Table 7.2 lists the commonly ordered laboratory tests specific to endocrine disorders.
| Laboratory Test | Normal Range | Indication |
|---|---|---|
| Adrenocorticotropic hormone (ACTH) | 9–52 pg/mL (picograms/milliliter) | Elevated level consistent with Addison's disease |
| Cortisol | 8–20 mcg/dL (micrograms/milliliter; drawn in am) | Decreased level consistent with Addison's disease |
| Glucose | 70–105 mg/dL (milligrams/deciliter; fasting) | Elevated level consistent with diabetes |
| Hemoglobin A1C (HbA1c) | 4.7–8.5% | Elevated levels consistent with diabetes |
| T4 | 0.9–2.4 ng/dL (free; nanograms/deciliter) 5–12 mcg/dL (total; micrograms/deciliter) |
Increased level consistent with hyperthyroidism |
| Thyroid-stimulating hormone (TSH) | 0.5–5.0 mcIU/mL (microinternational units per milliliter) | Decreased level consistent with hypothyroidism; increased level consistent with hyperthyroidism |
| Urinary free cortisol measurement | < 90 mcg (micrograms)/24 hours | Elevated levels consistent with Cushing’s syndrome |
Analysis of Nutrition and the Endocrine System
The endocrine system requires adequate nutrition to function. Nutritional deficits or imbalances can cause various endocrine abnormalities. For example, the most common cause worldwide for goiter, or an enlarged thyroid (Figure 7.4), is iodine deficiency as iodized salt is not consistently used worldwide (Can & Rehman, 2023). However, in the United States, its use has significantly reduced goiter development (Can & Rehman, 2023). Instead, goiter formation in the United States is usually caused by Hashimoto’s thyroiditis or Graves’ disease. Clients who primarily consume other types of salt (kosher, sea, etc.) need to obtain iodine in their diet through other means.
A thorough analysis of the client’s nutrition status can help identify potential endocrine-related issues. The nurse should review the nutritional assessment to identify any nutrient-related deficiencies. For example, a client with limited fruit and vegetable consumption is at risk for vitamin C deficiency. Vitamin C deficiency is associated with multiple health problems. Specifically related to the endocrine system, vitamin C affects the regulation of several important hormones including insulin growth factor and sex steroids (Shi, Rath, & Niedzwiecki, 2021). Conversely, when evaluating the client’s nutrition status, there is potential to find excessive intake of nutrients. For example, a diet with excessive carbohydrate intake can increase blood glucose levels in individuals contributing to the development of insulin resistance and diabetes. Once nutritional imbalances are identified, the nurse can work with the client to make dietary changes and reduce the risk for developing endocrine disorders (Bickley et al., 2021). Table 7.3 lists signs and symptoms of common endocrine disorders and their corresponding nutritional factors.
| Endocrine Disorder | Signs and Symptoms | Related Nutritional Factors |
|---|---|---|
| Diabetes | Increased thirst and urination, unexplained weight loss, increased hunger, blurred vision, slow-healing sores or infections, fatigue | Excessive intake of added sugar, refined grains, or overall calories can cause or worsen this condition |
| Hypothyroidism | Fatigue, weight gain, constipation, dry skin and hair, sensitivity to cold, depression, joint pain | Deficient iodine intake can cause or worsen this condition |
| Hyperthyroidism (Graves’ disease) | Weight loss, increased appetite, rapid heartbeat, trembling hands, nervousness or anxiety, sweating, heat intolerance | Excessive iodine intake can cause or worsen this condition |
| Adrenal insufficiency (Addison’s disease) | Fatigue, weakness, weight loss, nausea and vomiting, low blood pressure, darkening of the skin | High sodium diet is beneficial for clients with low aldosterone; adequate calcium and vitamin D intake is essential for clients taking corticosteroids |
| Cushing’s disease/syndrome | Weight gain, especially in the face, neck, and abdomen, thinning skin, easy bruising, slow healing of wounds, muscle weakness, fatigue | Controlled sodium diet and low-carbohydrate diet is beneficial |
Special Considerations
Obtaining Adequate Iodine through Diet Sources
Dozens of countries, including the United States, add iodine to table salt. Despite this practice, there are still groups who are at risk for iodine deficiency:
- People who do not use iodized salt including people in Southeast Asia, sub-Saharan Africa, and Eastern Europe
- Pregnant women
- Vegans and people who eat few or no dairy products, seafood, and eggs
- People living in areas with iodine-deficient soils – primarily mountainous areas (Himalayas, Alps, and Andes regions) or river valleys prone to flooding (South and Southeast Asia)
- People who consume foods that interfere with iodine uptake including soy, cassava, and cruciferous vegetables
Alternative sources of dietary iodine for these groups include:
- Seaweed (kelp, nori, kombu, and wakame) (traditionally consumed in China, Japan, and Korea)
- Fish and other seafood
- Dairy products
Fruits and vegetables, although they have a lot of other health benefits, are not a good source of iodine.
(source: NIH, 2023)
Unfolding Case Study
Part A
Read the following clinical scenario and then answer the questions that follow. This case study will evolve throughout the chapter.
Meena, a 44-year-old Indian American female was recently diagnosed with hypothyroidism and type 2 diabetes. She has a history of class 1 obesity, with a BMI of 33. Meena lives alone and works as an office administrator. Her hobbies include reading, watching movies, and cooking. Meena presents to the clinic complaining of fatigue and feeling cold even in warm temperatures.