From the Guidelines
Uncontrolled hypothyroidism can lead to numerous serious complications throughout the body if left untreated, including myxedema coma, cardiovascular complications, neuropsychiatric effects, reproductive issues, metabolic complications, gastrointestinal problems, musculoskeletal effects, and dermatologic manifestations. The most severe complication is myxedema coma, a life-threatening condition characterized by profound hypothermia, altered mental status, and respiratory depression requiring immediate treatment with intravenous levothyroxine (typically 300-500 mcg initially, followed by 50-100 mcg daily) 1. Some key complications of uncontrolled hypothyroidism include:
- Cardiovascular complications: increased risk of atherosclerosis, heart failure, and dyslipidemia with elevated LDL cholesterol levels
- Neuropsychiatric effects: depression, cognitive impairment, and peripheral neuropathy
- Reproductive issues: menstrual irregularities, decreased fertility, and increased risk of miscarriage
- Metabolic complications: weight gain, insulin resistance, and potential development of metabolic syndrome
- Gastrointestinal problems: constipation and decreased gut motility
- Musculoskeletal effects: muscle weakness, cramps, and joint pain
- Dermatologic manifestations: dry, coarse skin and brittle nails These complications develop because thyroid hormones regulate metabolism in virtually all body tissues, and their deficiency disrupts normal cellular function across multiple organ systems. Regular monitoring of thyroid function and proper levothyroxine replacement therapy (typically starting at 1.6 mcg/kg/day with dose adjustments based on TSH levels) are essential to prevent these complications 1.
From the FDA Drug Label
Maternal hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, gestational hypertension, pre‑eclampsia, stillbirth, and premature delivery. Untreated maternal hypothyroidism may have an adverse effect on fetal neurocognitive development
The complications of uncontrolled hypothyroidism include:
- Spontaneous abortion
- Gestational hypertension
- Pre-eclampsia
- Stillbirth
- Premature delivery
- Adverse effects on fetal neurocognitive development 2
From the Research
Complications of Uncontrolled Hypothyroidism
The complications of uncontrolled hypothyroidism can be severe and affect various systems in the body. Some of the complications include:
- Cardiovascular problems: Uncontrolled hypothyroidism can lead to an increased risk of atherosclerotic cardiovascular disease due to metabolic and hemodynamic effects 3. It can also cause heart failure, as seen in a case report where a 19-year-old girl presented with complete heart block and severe hyperlipidemia due to overt hypothyroidism 4.
- Infertility: Untreated hypothyroidism can lead to infertility, as mentioned in a study on the epidemiology and treatment of hypothyroidism 5.
- Myxedema coma: This is a life-threatening complication of untreated hypothyroidism, although it is rare 5.
- Mental retardation and delayed milestones: In infants, untreated hypothyroidism can lead to mental retardation and delayed milestones 5.
- Osteoporosis: Over-replacement of thyroid hormone can lead to an increased risk of osteoporosis, as mentioned in a study on the treatment of hypothyroidism 6.
- Atrial fibrillation: Over-replacement of thyroid hormone can also lead to an increased risk of atrial fibrillation 6.
Cardiovascular Complications
The cardiovascular complications of uncontrolled hypothyroidism can be significant. Some of the complications include:
- Atherosclerosis: Uncontrolled hypothyroidism can lead to an increased risk of atherosclerosis due to impaired lipid profile, low-grade chronic inflammatory state, increased oxidative stress, and increased insulin resistance 3.
- Ischemic heart disease: Hypothyroidism is a risk factor for ischemic heart disease, as mentioned in a study on hypothyroidism in patients with heart disease 7.
- Left and right ventricular dysfunction: Hypothyroidism can have a direct negative effect on both the left and right ventricular functions, leading to cardiomyopathy 7.
- Complete heart block: A case report mentioned a 19-year-old girl who presented with complete heart block due to overt hypothyroidism 4.