Hypothyroidism (underactive thyroid) occurs when a person produces insufficient amounts of thyroid hormone. The opposite of hypothyroidism is hyperthyroidism (also called overactive thyroid), a condition in which the body produces too much thyroid hormone and increases the body’s metabolism.
You can check your thyroid at home with a neck self-exam to help with early detection and check for lumps or enlargements in the neck that may indicate a potential thyroid condition.
You will need:
- A handheld mirror
- A glass of water
How to do a thyroid neck check:
- Hold the mirror in your hand, looking at the lower front area of the neck, above the collarbones, and below the voice box. The thyroid gland is located in this area of the neck.
- Don’t confuse the Adam’s apple with the thyroid gland. The thyroid gland is located further down on the neck, closer to the collarbone.
- Don’t confuse the Adam’s apple with the thyroid gland. The thyroid gland is located further down on the neck, closer to the collarbone.
- While focusing on this area in the mirror, tip your head back.
- Take a sip of water and swallow.
- While swallowing, check the neck for any bulges or protrusions in this area while swallowing.
- If you see any bulges or protrusions in this area, see your doctor.
- This may be a sign of an enlarged thyroid gland or a thyroid nodule and it needs to be checked to determine if treatment for thyroid disease is needed or if thyroid cancer is present.
What Is the Thyroid and What Does It Do?
The thyroid is a butterfly-shaped endocrine gland located below the Adam's apple in the lower part of the neck that wraps around the windpipe (trachea).
The thyroid plays a role in a number of bodily functions, including:
- Metabolism of fats, carbohydrates, proteins, electrolytes, and water
- Metabolic rate (oxygen consumption)
- Growth and development
- Resistance to infection
- Maintaining bone health
- Maintaining muscle control
- Vitamin requirements
- Preserving brain function and development
- Maintaining heart and digestive functions
- Reproduction
What Are Symptoms of Thyroid Problems?
Common symptoms of hypothyroidism (underactive thyroid) may include:
- Fatigue/lethargy
- Loss of energy
- Weight gain
- Weakness in extremities
- Decreased appetite
- Constipation
- Sleepiness
- Muscle pain
- Joint pain
- Dry skin
- Hair loss
- Mood swings
- Depression
- Mental impairment
- Cold intolerance
- Impaired memory/forgetfulness
- Mental impairment
- Difficulty concentrating
- Fertility problems
- Menstrual disturbances
- Decreased sweating
- Numbness and tingling and nerve entrapment syndromes
- Decreased hearing
- Mood swings
- Feeling of fullness in the throat
- Hoarseness
- Nail problems
Hyperthyroidism (overactive thyroid) may not cause any symptoms. When symptoms of hyperthyroidism occur, they may include:
- Anxiety
- Irritability
- Anger
- Trouble sleeping
- Sweating more than usual
- Heat intolerance
- Weakness
- Hand tremors
- Fast or uneven heartbeats
- Tiredness/fatigue
- Memory problems
- Weight loss even with a normal or increased appetite
- Diarrhea
- Frequent bowel movements
- Oily skin
- Hair thinning or hair loss
- Bulging eyes
- Watery eyes
- Eye redness or dryness
- Difficulty closing the eyelids
- Bulging eyes (if caused by Graves' disease)
- Swelling in the neck (goiter)
- Difficulty in hot weather, sweating when it’s not excessively hot, hot flashes
- Irregular or missed menstrual periods, which may be associated with infertility
- Breast tissue growth in men
- Erectile dysfunction (impotence)
- Atrial fibrillation, chest pain, and rarely, heart failure if untreated
Lumps or nodules on the neck may be a sign of thyroid cancer. See a doctor if you notice a lump on the neck.
How Are Thyroid Problems Diagnosed?
A doctor will take a medical history and perform a physical examination. Tests used to diagnose thyroid problems include:
- Blood tests:
- Thyroid-stimulating hormone (TSH)
- Thyroxine (T4)
- Triiodothyronine (T3)
- Thyroid antibody tests
- Thyroglobulin
- Calcitonin
- Carcinoembryonic antigen (CEA)
- Other blood tests such as complete blood count (CBC), tests for bleeding disorders, and tests to check liver and kidney function
- Thyroid scan
- Imaging tests
- Ultrasound
- Radioiodine scans
- Chest X-ray
- Computed tomography (CT) scan
- Magnetic resonance imaging (MRI) scan
- Positron emission tomography (PET) scan
- Fine needle aspiration biopsy
From 
https://www.hormone.org/your-health-and-hormones/glands-and-hormones-a-to-z/hormones/thyroid-hormones
https://www.uptodate.com/contents/hypothyroidism-underactive-thyroid-the-basics?search=Hypothyroidism&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1
https://www.uptodate.com/contents/hyperthyroidism-overactive-thyroid-beyond-the-basics?search=Hyperthyroidism&topicRef=15437&source=see_link
https://medicaltransformationcenter.com/what-are-early-warning-signs-of-thyroid-problems/
https://www.aace.com/disease-and-conditions/thyroid/how-check-your-thyroid#:~:text=Hold%20the%20mirror%20in%20your,drink%20of%20water%20and%20swallow.