History and exam

Key diagnostic factors

common

presence of risk factors

Key risk factors include female sex, middle age, family history of autoimmune thyroiditis, autoimmune disorders, treatment for thyroid disease, postpartum thyroiditis, Turner and Down syndromes, radiotherapy to head and neck, iodine deficiency, amiodarone use, and lithium use.

non-specific symptoms

Patients may have no symptoms or vague, non-specific symptoms (e.g., feeling slow) that are often clinically overlooked.[50]

Other diagnostic factors

common

lethargy

Non-specific, may be predominant symptom.​[52][54]​​ Other terms used are fatigue or tiredness.

constipation

May be related to reduced motility of the gastrointestinal tract.[1]​​[52]

weight gain

May be persistent despite thyroid hormone replacement therapy.[2]​​

depression

Frequent symptom in people with overt hypothyroidism, and in one study prevalence was found to be 63.5% in people with sub-clinical hypothyroidism.[58]​ Depressive symptoms due to hypothyroidism usually respond to thyroid hormone replacement therapy, but may be persistent.[2][58]​ 

menstrual irregularity

Menstrual irregularity occurs in approximately one third of women with hypothyroidism.[59] Oligomenorrhoea, polymenorrhoea and amenorrhoea are all​ reported more frequently in women with hypothyroidism than in the general population. Patients may also present with infertility.[1][59]​​

dry or coarse skin

Reported by 63% of patients in one study.[52]

change in voice

A change in voice (e.g., hoarser, deeper) is commonly seen.[2]​​[53]

bradycardia

Commonly reported.[2]​​

hypertension

Diastolic hypertension predominates.[60][61]​​​

delayed relaxation of tendon reflexes

Commonly reported.[1]​​

cold sensitivity

Commonly reported.[2]​​[52]

uncommon

coarse hair

May be noted.[53]

eyelid oedema

May be present.[53]

goitre

Goitre is more common in areas of iodine deficiency and may also be present in autoimmune (Hashimoto) thyroiditis.​[12][17]​​​[25]

Risk factors

strong

iodine deficiency

Iodine intake is still insufficient in some countries, increasing the risk of iodine deficiency in these populations.​[12] IGN: global scorecard of iodine nutrition 2023 Opens in new window Pregnant women have an increased risk of iodine deficiency, especially in the first and second trimesters.[14] IGN: global scorecard of iodine nutrition 2023 Opens in new window​​​​​​ 

female sex

Autoimmune (Hashimoto's) thyroiditis, the most common cause of primary hypothyroidism in the US, is up to 9 times more common in women than men.[15][16]​ Pregnant women have an increased risk of primary hypothyroidism due to increased iodine requirements which may lead to iodine deficiency.[14] IGN: global scorecard of iodine nutrition 2023 Opens in new window​​

middle age

Autoimmune thyroiditis has a peak incidence in people aged 30-50 years.[15]

family history of autoimmune thyroiditis

Autoimmune thyroiditis is more common in relatives of affected patients.[17]​ The genetics have autosomal dominance and polygenic features.​[5]​​[17]

autoimmune disorders

Autoimmune thyroiditis is associated with other autoimmune disorders such as vitiligo or Sjogren's syndrome, and multiple endocrine deficiency, which can cause hypoparathyroidism, adrenal failure, ovarian failure, and type 1 diabetes mellitus.​​[17][29]

treatment for thyroid disease

Primary hypothyroidism may follow radioiodine ablation therapy or surgery for thyroid disease (e.g., Graves' disease, toxic nodular disease).[2][31]​​[32][33]

post-partum thyroiditis

Has variable clinical course of hyperthyroidism or hypothyroidism usually followed by spontaneous resolution. Approximately 30% of women affected will remain hypothyroid one year post-partum.[34]

Turner and Down syndromes

Autoimmune thyroiditis is more common in people with Turner syndrome or Down syndrome compared with the general population.[2]​​[35]

radiotherapy to head and neck

Hypothyroidism is common after radiotherapy for head and neck cancer.​[40]​​

amiodarone use

Meta-analyses have estimated that 14% to 23% of patients treated with amiodarone develop hypothyroidism.[42][43][44]​​​ Amiodarone contains a high iodine load, which can interfere with thyroid hormone synthesis.​[30]​​

lithium use

Lithium decreases thyroid hormone synthesis and blocks thyroid hormone release.[1]​​[19]

laryngectomy

Systematic review evidence suggests that overall hypothyroidism is seen in 49% of patients post-laryngectomy. Risk is increased with more extensive surgery and with combination therapy: for example, the rate of hypothyroidism after laryngectomy with hemithyroidectomy and radiotherapy is 65%, compared with 11% after laryngectomy alone.[45]

treatment for multidrug-resistant tuberculosis (TB)

Drugs used for the treatment of multidrug-resistant TB have been associated with a pooled prevalence of hypothyroidism of 17%.[46]​ Ethionamide and para-aminosalicylic acid were the most common causative drugs. Thyroid function generally normalises within a few weeks of stopping treatment.[47]

weak

type 1 diabetes

It is estimated that 8% to 44% of patients with type 1 diabetes mellitus develop autoimmune thyroiditis, which may progress to hypothyroidism.[36][37]​​​​[38][39]

infiltrative disease

Rarely, infiltrative diseases such as sarcoidosis can cause primary hypothyroidism.[2]​​

iodine excess

Autoimmune thyroiditis is more common in populations with high dietary iodine, which is thought to make the thyroid more antigenic.[27][28]

exposure to pesticides

Herbicides and organochlorine, organophosphate, and pyrethroid insecticides have been associated with increased risk of hypothyroidism.[41]

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