Hyperthyroidism & Hypothyroidism

Know the signs.

In healthy individuals, the thyroid gland, located in the neck, is responsible for regulating the metabolism by way of the hormones thyroxine and triiodothyronine.1 Normally,
the hypothalamus gland, located in the brain, secretes a thyroid-releasing hormone that signals the pituitary gland, aka the master gland, to secrete thyroid-stimulating hormone (TSH), which then signals the thyroid to
produce thyroxine and triiodothyronine.2
Thyroid hormones play vital roles in regulating the body’s metabolic rate, heart and digestive functions, muscle control, brain development and function, and the maintenance of bones. In some cases, however, the thyroid can become imbalanced in its hormone production, which can result in the development of hyperthyroidism or hypothyroidism.3,4 In hyperthyroidism, the thyroid produces too much of its hormones, and in hypothyroidism, the thyroid does not produce enough.2 Women are more likely than men to develop either of these thyroid conditions.5,7

Hyperthyroidism.

Hyperthyroidism has several causes, with the most common one being Graves’ disease, an autoimmune disorder in which the immune system attacks the thyroid and causes it to make more thyroid hormone than the body needs.8 The overproduction of thyroid hormone by a single or by multiple thyroid nodules, as well as excessive intake of the thyroid hormone supplement, levothyroxine, can also lead to hyperthyroidism.8 Hyperthyroidism is between 2 and 10 times more common in women than in men.7

Symptoms. Symptoms of hyperthyroidism include unintentional weight loss (but not necessarily loss of appetite); rapid heart rate (more than 100 beats a minute); irregular or pounding heart beat; increased appetite; nervousness, anxiety, and/or irritability; hand tremors; sweating; changes in menstrual cycle; increased sensitivity to heat; changes in bowel patterns, especially more frequent bowel movements; enlarged thyroid gland (goiter); fatigue; muscle weakness; difficulty sleeping; skin thinning; and fine, brittle hair. Older adults who develop hyperthyroidism might not have any symptoms or only very subtle ones. A doctor’s visit is in order if you’ve been feeling tired for no reason and/or have any of the other symptoms associated with hyperthyroidism.9

Hypothyroidism.

Hypothyroidism is the second most common endocrine system disorder among women and the most common pregnancy-related thyroid disorder (affecting 3–5% of all pregnant women).3,10 Hypothyroidism is approximately six times more common in women than in men,5 and is predominantly caused by the presence of a condition called Hashimoto’s thyroiditis, an inflammation of the thyroid gland caused by antithyroid antibodies.8 Prior treatment for Graves’ disease by way of surgery or radioiodine can also result in hypothyroidism.8 Less often, hypothyroidism can be caused by too much or too little iodine in the diet due to pituitary disease.11 Newborn infants can also present with congenital hypothyroidism; however, though this condition is perhaps the most common metabolic disorder in infants, it is relatively easy to treat compared with other metabolic or hereditary diseases. Many babies will require life-long treatment, but for some babies, congenital hypothyroidism is temporary, and treatment need only take place for the first few years of life 12 ,13

Symptoms. Symptoms of hypothyroidism tend to develop slowly, over a number of
years, progressively becoming more serious. These symptoms include weight gain; fatigue; puffy face; muscle weakness and or aches; joint stiffness/swelling; constipation; dry skin; hoarseness; high cholesterol; thinning hair; slowed heart rate; depression; memory problems; and enlarged thyroid gland (goiter). A doctor’s visit is in order if you’ve been feeling tired for no reason and/or have any of the other symptoms associated with hypothyroidism.14

Diagnosis and treatment.

Whenever someone has any one or a combination of the above described symptoms, a suspicion of thyroid dysfunction must first be considered. Thyroid dysfunction is progressive, with milder forms eventually progressing to more advanced forms.8 Thus, it is important for people who show early signs of thyroid dysfunction to get screened or tested as early as possible in order to identify and begin treatment before they develop the more severe complications of hyperthyroidism, hypothyroidism, or other thyroid conditions.8

Consequences untreated hyperthyroidism include atrial fibrillation (irregular, rapid heart rate), congestive heart failure, osteoporosis, and/or neuropsychiatric disorders,8 while those attributed to unmanaged hypothyroidism include heart damage, central nervous system damage, and psychiatric illnesses like depression, psychosis, delirium, and dementia.15 Hyperthyroidism is commonly treated with medication, such as beta-blockers and antithyroid drugs, radioiodine therapy, and/or thyroid surgery.7 Hypothyroidism treatment is typically treated with a hormone replacement supplement, most commonly levothyroxine.11

Other notable thyroid conditions.

Thyrotoxicosis is a condition that involves the excess circulation of thyroid hormones, but this is not necessarily linked with thyroid dysfunction. Causes include thyroiditis (inflammation of the thyroid), iodine-induced or drug-induced thyroid dysfunction, and ingestion of excess thyroid hormones.4 Thyrotoxicosis can be treated using antithyroid drugs, radioactive iodine, or surgery.16 Thyroid storm is another notable condition and is a severe stage of hyperthyroidism that is characterized by exaggerated signs and symptoms of hyperthyroidism, varying degrees of organ decompensation,17 and myxedema coma, which is the most severe manifestation of hypothyroidism, characterized by a lack of energy that evolves into stupor and eventually coma with associated respiratory failure and hypothermia.18

SOURCES

1. Mullur R, Liu YY, Brent GA. Thyroid hormone regulation of metabolism. Physiol Rev. 2014;94(2):355–382.

2. Holcomb SS. Thyroid diseases: a primer for the critical care nurse. Dimens Crit Care Nurs. 2002;21(4):127–133.

3. Dunn D, Turner C. Hypothyroidism in women. Nurs Womens Health. 2016;20(1):93–98.

4. De Leo S, Lee SY, Braverman LE. Hyperthyroidism. Lancet. 2016;388(10047):906–918.

5. Nygaard B. Hypothyroidism (primary). BMJ Clin Evid. 2014;2014. pii: 0606.

7. National Institute of Diabetes and Digestive and Kidney Diseases site. Hyperthyroidism (Overactive Thyroid). https://www.niddk.nih.gov/ health-information/endocrine-diseases/hyperthyroidism. Accessed Accessed 27 Nov 2018.

8. Helfand M. Appendix B: Screening for thyroid disease: systematic evidence review. In: Stone MB, Wallace RB (eds). Institute of Medicine (US) Committee on Medicare Coverage of Routine Thyroid Screening: Medicare Coverage of Routine Screening for Thyroid Dysfunction. Washington DC: National Academies Press (US); 2003.

9. Mayo Clinic site. Hyperthyroidism (overactive thyroid) Nov. 03, 2018. https://www.mayoclinic.org/diseases-conditions/hyperthyroidism/ diagnosis-treatment/drc-20373665. Accessed 5 Dec 2018.

10. TengW,ShanZ,Patil-SisodiaK,CooperDS.Hypothyroidismin pregnancy. Lancet Diabetes Endocrinol. 2013;1(3):228–237.

11. NationalInstituteofDiabetesandDigestiveandKidneyDiseasessite. Hypothyroidism (Underactive Thyroid). https://www.niddk.nih.gov/ health-information/endocrine-diseases/hypothyroidism. Accessed 27 Nov 2018.

12. SrinivasanS,MisraM.Hyperthyroidisminchildren.PediatrRev. 2015;36(6):239–248.

13. KollatiY,AmbatiRR,ReddyPN,etal.Congenitalhypothyroidism:facts, facets & therapy. Curr Pharm Des. 2017;23(16):2308–2313.

14. Mayo Clinic site. Hypothyroidism (underactive thyroid). Dec. 04, 2018. https://www.mayoclinic.org/diseases-conditions/hypothyroidism/ symptoms-causes/syc-20350284. 5 Dec 2018

15. Kandukuri RC, Khan MA, Soltys SM. Nonadherence to medication in hypothyroidism: a case report. Prim Care Companion J Clin Psychiatry. 2010;12(3). pii: PCC.09m00863.

16. Pearce EN. Diagnosis and management of thyrotoxicosis. BMJ. 2006;332(7554):1369–1373.

17. ChihaM,SamarasingheS,KabakerAS.Thyroidstorm:anupdated review. J Intensive Care Med. 2015;30(3):131–140.

18. RizzoLFL,ManaDL,BrunoOD,WartofskyL.[Myxedemacoma]. Medicina (B Aires). 2017;77(4):321–328. Article in Spanish.

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