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Iodine deficiency—when severe—is the world’s leading cause of preventable hypothyroidism.²⁹  Deficiency of selenium and the presence of adverse chemicals (perchlorates, thiocyanates) worsen the problem.  Milder iodine deficiency causes an enlarged thyroid gland (goiter) without frank hypothyroidism (as Kocher discovered).³⁰ In fact, in mild iodine deficiency, plasma T3 can be increased.³¹ 

Clinicians can expect to see other causes.  High iodine causes pseudo-hypothyroidism.³²  The gland becomes TSH-resistant to protect itself from high iodine-exposure.³³  Lithium at doses used to treat type-I bipolar disorder cause toxic hypothyroidism in up to 20% of users by its effects on iodine-uptake into the gland and its “organification.”  However, lithium in these amounts more often produces a marked multinodular goiter.^34,35  (Lithium supplementation up to 10 mg daily seems safe.³⁶)

Diagnosis of Hypothyroidism

Before starting to treat hypothyroidism, one must make a correct diagnosis.  Mindful that the problem is common, we identify patients who are at-risk by their symptoms and physical examination. 

Symptoms

Endocrine symptoms are notoriously non-specific—so that authoritative guidelines actually discourage the use of questionnaires.³⁷  However, we have been told that “patients who report multiple thyroid symptoms warrant thyroid testing.”² Therefore I use a questionnaire, the severity of each symptom being graded from 0 to 4 by the patient (free on request).³⁸  It also provides a “baseline” inventory, against which the patients’ progress (or lack thereof) later can be compared. 

Be cautious about interpreting symptoms: Many symptoms of hypothyroid function are also symptoms of high thyroid function.  We will later examine some of the physiological reasons for this.  Patients with either high or low thyroid hormone levels can complain of the following:

• Fatigue                       
• Heart palpitations
• “Brain fog”    
• Irritable bowel
• Hair loss                     
• Muscle weakness
• Urticaria                     
• “Joint stiffness”
• Insomnia                    
• Anxiety, irritability
• Menstrual irregularities… and more.

It should also be remembered that some patients can be symptom-free…or wholly unaware of them.  A patient with a palpably “bad” thyroid gland whose labs repeatedly showed TSH over 50 with low freeT4 denied any symptom.  She finally agreed to try my treatment.  On her return six weeks later, she was embarrassed to admit her co-workers were commenting on how bright and alert she had become and had been asking her what she was doing differently. 

Before closing this section, remember that failing spontaneous remission, the end-stage of Graves’ disease (high thyroid) is low-thyroid function.  Ask your people about a remote history of Graves’ symptoms, including a huge appetite without weight gain; being underweight; having felt hot or tremulous etc.³⁹  This history may influence treatment outcome. 

Physical Examination

The physical exam is important; yet, after I’ve palpated their thyroid gland, many patients ask me what I had done, saying that nobody had ever examined them there.  I am also dismayed by the prevalence of internet images showing practitioners supposedly examining the thyroid gland but nowhere near it—even on sites dedicated to the thyroid gland!  Look at a diagram of thyroid anatomy: One of the best (unexpectedly) is on Pinterest.⁴⁰ 

Operating many times on and around the thyroid gland has made me confident of finding it in the neck.  I and others⁴¹ examine patients face-to-face with the neck in a neutral position, not hyper-extended—this relaxes the strap muscles covering the gland.  Place one thumb on the patient’s “Adam’s apple” (for purists: the laryngeal prominence of the thyroid cartilage).  Place the other thumb on the cricoid cartilage (about 2 cm lower) …these landmarks are easily found; no worries.

Noting the distance between your thumbs, drop the upper thumb from the Adam’s apple to an equal distance below your cricoid thumb and nestle it in.  It now rests on the trachea, below the thyroid isthmus—that’s the spot!  Now, put your cricoid thumb next to it, one on either side of the trachea and glide them up together.  Before you get to the cricoid, you’ll feel a “blip” as the thyroid gland slides under your questing thumbs.  When you have identified the isthmus, circle about with your thumbs and palpate the lobes of the thyroid “bow tie.”

What should we do when the larynx is ptotic and the gland is hidden behind the medial heads of the clavicles…or when it is buried deeply within an unusually stout neck?  Keep your thumbs just below the cricoid and ask the patient to swallow.  The thyroid gland is fixed to the laryngo-tracheal apparatus.  With a swallow, the gland rises out of the depths and is palpable in its passage. 

It is fine with me if your fingertips are more discerning than your thumbs: Alton Ochsner taught Tulane medical students to examine the thyroid gland from behind the patient.  The excellent University of Washington web site is correct—this is a valid method, if you are examining the right spot.⁴¹  

What should we expect to find?  A healthy thyroid gland should be nearly as velvety as a lipoma.  On examination, the inner voice says: “There it was, I think.”  A pediatric endocrinologist in my highest esteem has said we cannot feel a child’s normal thyroid gland at all.  Adult or child, when the gland is distinctly palpable, it is—to some extent—abnormal.  If you can say “The thyroid is right here,” it is probably unhealthy—and a biopsy usually shows fibrosis.⁴² 

As a rookie surgeon, I once thought hypothyroid people would have goiters. That’s wrong; do NOT expect a big goiter—glands with lymphocytic thyroiditis are often smaller than normal.⁴³  The worst glands can feel like a piece of over-cooked liver—firm but usually not enlarged.  Following palpation, the skin over the thyroid can flush redly for many minutes afterwards, a sign I associate with autoimmune thyroiditis. 

Sometimes we can feel nodules, single or multiple, which take us beyond the scope of today’s subject.  Please know how to work them up.  An authoritative guideline is free to download.⁴⁴ 

Occasionally, a diseased gland feels perfectly normal on exam.  This makes other, “secondary” signs of hypothyroidism more valuable.  Is your patient overly-dressed for the ambient temperature? A wool sweater in July is a clue!  Check for cold hands and fingers; flaky, raggedy fingernails; a slow pulse or a sluggish biceps brachii reflex.  Thinning hair is a common complaint, which is usually “relative” but often noticed by their hairdresser.  Less commonly, the lateral one-third of eyebrows can be disappearing; or there may be puffy eyes and signs of “myxedema” (the 19^th century name for hypothyroidism before the thyroid gland was understood). 

Most Graves’ patients (many of whom are subclinical and not diagnosed)^45,46 end up hypothyroid.  Is your patient oddly slender?  Observe their eyes but remember: Inferior scleral show can be “normal” and the diagnosis of proptosis is made properly with an exophthalmometer.^47,48 

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