# Hypothyroidism --- **Hypothyroidism** or sometimes called an "underactive thyroid" is a [[disease]] where [[thyroid]] is unable to make enough [[thyroid hormone]] to keep the body running properly. Since thyroid hormone is important to regulating our metabolism—specifically our [[basal metabolic rate]]—not enough TH can cause our energy and other basic functions to drop. Hypometabolic state brings on weakness and fatigue, cold intolerance, dry skin, constipation, etc. Ironically there is a weight gain despite the loss of appetite. ## Causes There are multiple reasons that might cause hypothyroidism. - The most common cause is an [[autoimmune disorder]] called **Hashimoto's disease** - an example of a [[type II hypersensitivity|type 2 hypersensitivity]] reaction - due to a *lack* of dietary [[iodine]] - Uncommon in the USA - The [[pituitary gland]] keeps sending [[thyroid hormone|thyroid stimulating hormone]], but the [[thyroid]] simply cannot make it without iodine. It keeps trying and trying, but can't do anything, and can develops a **goiter**. - due to an *excess* of iodine. - I don't know why on this one, i think it just overworks the thyroid to exhaustion - thyroiditis, or an inflammation of the [[thyroid]] - surgical removal/radiation treatment of the head/neck - some medicines - lithium, iodine compounds, anti-thyroid meds - atrophy of the thyroid due to aging - infiltrative disease of the thyroid - [[amyloidosis]] - [[lymphoma]] - [[scleroderma]] ## Risk Factors - sex - AFAB 5-8x more likely to get it - age - most common between the ages of 30 and 60 - the thyroid can atrophy with age - insufficient dietary [[iodine]] ## Signs & Symptoms The first signs of hypothyroidism are irritability and fatigue. As the disease progresses emotional responses are less apparent. If left untreated the later symptoms are mental dullness, thick tongue/slow speech, appearing apathetic. A broad overview of symptoms are: - tiredness/fatigue - depression - hypoglycemia - hypovolemia - hypotension - hypoventilation - bradycardia - [[constipation]] - dry skin - puffy face - muscle weakness - muscle aches - thinning hair ### Myxedema **Myxedema** is a type of nonpitting edema in the [[connective tissue]] seen throughout the body but especially in the face. It's caused by a buildup of a hydrophilic mucopolysaccharide mucus (which is quite gunky). It results in things like: - thick tongue - hoarse, husky voice - carpal tunnel - muscle cramps, stiffness/pain Treatment for myxedema include: - monitor for [[altered mental status]] - don't give sedatives - check vitals - IV[[thyroid hormone|T4]] administered cautiously - may need support for cardiorespiratory system - intubation - IV fluids - give blankets, but not electric blankets/heating pads - heating pads can cause vasodilation which makes BP worse A **myxedema coma** is a very bad, life-threatening sign, often brought on as a result of an infection or other systemic condition, rendering someone unconscious and *hypothermic*. - hyponatremia - hypoglycemia - hypovolemia - hypotension - hypoventilation - bradycardia ### Thyroid Changes During Pregnancy • Thyroid increases in size • 50% increase in thyroxine (T ) and triiodothyronine (T ) levels • Many signs and symptoms of thyroid disorders (e.g., nausea, anxiety, fatigue, and increased heart rate) are also common complaints during pregnancy • Careful assessment of symptoms is critical to early diagnosis and intervention to prevent fetal and maternal harm • Hypothyroidism Occurs in 2 to 12 pregnancies per 1000 • Usually caused by glandular destruction by autoantibodies (Hashimoto thyroiditis) • Characteristic symptoms: Weight gain • Lethargy • Decrease in exercise capacity • Cold intolerance • Constipation • Hoarseness • Hair loss • Brittle nails • • Dry skin • • • Fetus depends on pregnancy thyroid hormones until approximately 18 weeks of gestation Normal T levels early in pregnancy are important for proper fetal brain development Normalizing thyroid function by mid-pregnancy avoids neurodevelopmental deficits in children Untreated hypothyroidism increases risk for: Miscarriage Preeclampsia Placental abruption Preterm birth Stillbirth Low birthweight Infertility Curriculum Committee and Social Media • Laboratory values: elevated levels of TSH, with or without low T 4 levels • Treatment: • Levothyroxine (e.g., T 4 [Synthroid]) • Usual beginning dosage is 25 mcg/day • Adjustment by 25 to 50 gg every 4 to 6 weeks as necessary based on the TSH level • Maintain the TSH level at the lower end of the normal range • Increased doses of thyroid hormone are usually required as pregnancy progresses, probably related to increased estrogen levels • Will likely continue treatment with levothyroxine postpartum. Treatment is safe with breastfeeding ## Diagnostic Tests - blood draw - [[thyroid hormone|TSH]] will be high but [[thyroid#Physiology|T4]] will be low ## Treatment It's pretty much just taking [[levothyroxine]]. ___