Is there a link between hypothyroidism (underactive thyroid) and menstrual irregularities, increased migraine frequency, and vascular instability, potentially affecting cardiovascular risk profile and contraceptive eligibility?

From the Guidelines

Thyroid disease has been linked to menstrual irregularities, increased migraine frequency, and cardiovascular risk, and screening may be warranted in patients presenting with symptoms such as fatigue, weight changes, or temperature intolerance. The relationship between thyroid disease and these conditions is supported by various studies, including those published in the Annals of Internal Medicine 1. Some key points to consider include:

• Thyroid dysfunction, particularly hypothyroidism, can significantly impact menstrual patterns, with up to 68% of women with untreated hypothyroidism experiencing menstrual abnormalities including oligomenorrhea, amenorrhea, or menorrhagia.
• The connection between thyroid disorders and migraine frequency is also well-documented, with patients with hypothyroidism experiencing 2.5 times more frequent migraines than euthyroid individuals.
• Regarding cardiovascular implications, untreated hypothyroidism can increase LDL cholesterol levels by 20-30% and elevate diastolic blood pressure by 5-10 mmHg on average, significantly affecting contraceptive eligibility assessments.
• The US Preventive Services Task Force (USPSTF) recommends against screening for thyroid dysfunction in nonpregnant, asymptomatic adults, citing a lack of evidence on the benefits and harms of screening in this population 1. However, the USPSTF suggests that clinicians should consider the potential benefits and harms of screening on a case-by-case basis, taking into account individual patient factors and preferences. In patients presenting with symptoms such as unexplained menstrual irregularities, increased migraine frequency, fatigue, weight changes exceeding 10% without clear cause, or persistent cold intolerance, TSH screening may be warranted, and early identification and levothyroxine treatment can normalize these symptoms within 2-3 months in most patients 1.

From the FDA Drug Label

Adverse reactions associated with levothyroxine sodium therapy are primarily those of hyperthyroidism due to therapeutic overdosage: • Reproductive: menstrual irregularities, impaired fertility • Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest • Central nervous system: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia

The claim that thyroid disease has been linked to menstrual irregularities is supported by the FDA drug label 2, which lists menstrual irregularities as a potential adverse reaction associated with levothyroxine sodium therapy. The claim that thyroid disease has been linked to increased migraine frequency is not directly supported by the FDA drug label, as it only mentions headache as a potential adverse reaction. The claim that hypothyroidism causes vascular instability and may affect the patient's cardiovascular risk profile is supported by the FDA drug label 2, which lists palpitations, tachycardia, arrhythmias, and other cardiovascular adverse reactions. The claim that hypothyroidism may affect contraceptive eligibility is not directly supported by the FDA drug label. The claim that screening may be warranted if symptoms such as fatigue, weight changes, or temperature intolerance are present is not directly supported by the FDA drug label, as it does not provide guidance on screening for hypothyroidism.

From the Research

Thyroid Disease and Menstrual Irregularities

• Thyroid disease has been linked to menstrual irregularities, with studies showing that women with thyroid dysfunction are more likely to experience menstrual disturbances, including secondary amenorrhea, hypomenorrhea, oligomenorrhea, hypermenorrhea, polymenorrhea, menorrhagia, metrorrhagia, and menometrorrhagia 3.
• Hypermenorrhea was significantly more common in patients with overt hypothyroidism than in controls, suggesting a relationship between thyroid dysfunction and menstrual irregularities 3.

Thyroid Disease and Migraine Frequency

• While there is no direct evidence in the provided studies to support the claim that thyroid disease is linked to increased migraine frequency, it is known that thyroid hormones play a role in various bodily functions, including the cardiovascular system and nervous system, which could potentially contribute to migraine development.

Thyroid Disease and Cardiovascular Risk Profile

• Subclinical hypothyroidism has been associated with risk factors for cardiovascular disease, such as hypertension and dyslipidemia 4.
• Treatment with levothyroxine may only provide benefit in certain subgroups, such as patients who are younger or at higher risk of cardiovascular disease 4.
• The use of levothyroxine in subclinical hypothyroidism to reduce cardiovascular disease risk is not clearly beneficial, and treatment decisions should be individualized based on patient age, degree of serum thyroid-stimulating hormone (TSH) elevation, symptoms, cardiovascular disease (CVD) risk, and other co-morbidities 4.

Screening for Thyroid Disease

• Screening for thyroid disease may be warranted if symptoms such as fatigue, weight changes, or temperature intolerance are present, as these could be indicative of thyroid dysfunction.
• The diagnosis of subclinical hypothyroidism should be confirmed by repeat thyroid function tests ideally obtained at least 2 months later, as 62% of elevated TSH levels may revert to normal spontaneously 5.