Thyroid disorders affect all areas of your body. Your thyroid gland, at the front of your neck, makes tri-iodothyronine (T3) and thyroxine (T4) hormones, which regulate metabolism. T3 is the active version of the hormone. T4 is also converted into T3 by the tissues and organs that use it. Normally, T3 and T4 production is regulated by thyroid-stimulating hormone (TSH), which is produced in the pituitary gland in the brain.
This article was included in issue 101 (Summer 2024) of The Menopause Exchange newsletter.
Underactive thyroid
An underactive thyroid (hypothyroidism) affects around 12% to 20% of women over 60. It’s often caused by autoimmune thyroid disease (‘Hashimoto’s disease’). The body’s immune system mistakenly sees thyroid tissue as foreign and damages it, reducing hormone production. Hypothyroidism may result from treatments for an overactive thyroid or thyroid cancer, including thyroid surgery or radioactive iodine. If there isn’t enough circulating T4, the metabolism slows down, causing symptoms such as tiredness, weight gain, dry hair/skin, constipation, anxiety, low mood, poor concentration and memory problems.
An underactive thyroid can be difficult to diagnose from symptoms alone, as these are often vague and similar to other conditions, so thyroid disorders are also diagnosed using thyroid function blood tests. These tests may give a ‘borderline’ result if other conditions have affected thyroid function, such as a viral infection. Your GP can arrange a repeat test; if your levels have returned to normal, it’s unlikely you have a thyroid problem.
If your hormone levels remain borderline or worsen, you may have subclinical hypothyroidism, which can progress to an underactive thyroid. Your GP may start low dose treatment to see if this helps. If your thyroid gland is swollen or there’s a lump, you may need scans. Hypothyroidism treatment usually involves thyroid hormone replacement supplements. Levothyroxine is the most commonly prescribed in the UK.
Overactive thyroid
An overactive thyroid (hyperthyroidism), affects around 1.5% of women of menopausal age. The two main causes are an autoimmune thyroid disease (Graves’ disease) and benign (non-cancerous) thyroid nodules, which can release excess thyroid hormone.
With excessive circulating thyroid hormone, the body’s metabolism speeds up, causing fatigue, sweating, heat intolerance, weight loss, difficulty sleeping, shaking, heart palpitations (fast or irregular heartbeat) and anxiety. Graves’ disease may also cause gritty sore eyes, eyeball protrusion and visual problems.
Initial hyperthyroidism management is usually supervised by an endocrine specialist, and includes antithyroid drugs, radioiodine treatment or surgery.
Menopause symptom overlap
The risk of developing an underactive thyroid gland increases with age. It’s not unusual for women going through menopause to also have an underactive thyroid. Symptoms of both hypothyroidism and the menopause are similar, can be non-specific and may overlap, so it’s important for your GP to do thyroid function blood tests before attributing symptoms solely to the menopause.
Once hypothyroidism has been diagnosed, you may be initially stable on levothyroxine. However, changing oestrogen levels during the menopause can affect your levothyroxine requirements. Regular reassessment, every 6 to 12 months, is needed to check you’re on the correct dose of levothyroxine, or more frequently if your symptoms worsen.
Hormone replacement therapy (HRT) is a first-line treatment for menopausal symptoms and usually has no impact on thyroid function if there’s no underlying thyroid disease. Thyroxine supplements aren’t a contraindication to HRT, but oestrogen can affect levels of thyroxine in the blood, with subsequent lower levels of available thyroid hormone. Therefore, women should have blood tests to check their thyroid function after starting oral combined HRT. If necessary, their GP will increase the levothyroxine dose. Gel, patch or spray oestrogen therapies don’t usually affect thyroxine doses.
Falling oestrogen levels can lead to a loss of bone density and increased fracture risk. Hyperthyroidism and overtreated hypothyroidism are also associated with increased fracture risk, so good management is important. It’s not clear if subclinical hyperthyroidism poses a risk as well, but a regular review is advised.
Oestrogen and progesterone can bind to thyroid hormone and prevent absorption so you should take HRT and levothyroxine at least an hour apart. Levothyroxine should preferably be taken on an empty stomach as it’s affected by food, milk, tea or coffee. If you’re taking calcium carbonate supplements, keep them four hours clear of levothyroxine supplements.
Before taking complementary, herbal or ‘natural’ menopausal treatments, discuss your plan with your pharmacist or doctor, especially if you have any long-term conditions or take medication, including but not only for thyroid conditions. Using phytoestrogens is now commonplace for the menopause, either as supplements or in food, but soy may reduce thyroxine absorption. Women taking levothyroxine and using soy products should avoid eating or drinking soy products for four hours before or after taking their levothyroxine medication. If they have high dietary soy intakes, they should have regular thyroid function tests to assess any changes in their levothyroxine requirement.
The minimal evidence available suggests that women with normal thyroid function, who don’t take thyroxine supplements, aren’t affected by soy intake. But high dietary soy isoflavones have been shown by some studies to possibly raise TSH and T3 levels, especially in women. So they should alert their GPs to any related symptoms.
About the author
Dr Gill Jenkins is a GP in the Bristol area. She has an interest in women’s health, diabetes and lifestyle health.
Created Summer 2024
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