Thyroid Health for Women: Symptoms, Testing, and Nutritional Support
Thyroid dysfunction is the most common hormonal issue in women, affecting an estimated 1 in 8 over their lifetime. Hypothyroidism, particularly autoimmune Hashimoto's thyroiditis, is consistently underdiagnosed because TSH-only testing misses subclinical dysfunction, and symptoms are attributed to depression, anxiety, or the vague category of "stress."
The Thyroid and Women's Hormones
The thyroid regulates metabolism in every cell of the body. It is deeply connected to the reproductive hormonal system: hypothyroidism impairs progesterone production, disrupts oestrogen metabolism, affects cortisol regulation, and is strongly associated with PMDD, heavy periods, fertility challenges, and worsening perimenopausal symptoms.
Hashimoto's Thyroiditis
Hashimoto's is an autoimmune condition in which the immune system attacks the thyroid gland. It is the most common cause of hypothyroidism in women and is driven by multiple factors including genetic predisposition, gut permeability (leaky gut), nutritional deficiencies, and environmental triggers. Importantly, antibody levels can be elevated years before TSH shifts out of range, and symptoms are present throughout [1].
Symptoms of Hypothyroidism
• Fatigue that does not improve with rest
• Weight gain despite unchanged diet and activity
• Cold intolerance
• Constipation
• Brain fog and poor concentration
• Depression and low mood
• Hair loss or thinning
• Dry skin
• Heavy or irregular periods
• Low basal body temperature
• Slow reflexes
Getting the Right Testing
Standard TSH-only testing is inadequate for identifying thyroid dysfunction early. A full thyroid panel includes:
• TSH (thyrotropin)
• Free T4 (free thyroxine)
• Free T3 (free triiodothyronine, the active form)
• Reverse T3 (rT3, which can block T3 activity)
• TPO antibodies (thyroid peroxidase, Hashimoto's marker)
• TG antibodies (thyroglobulin, Hashimoto's marker)
See the full article on hormone testing for optimal reference ranges and how to interpret results clinically.
Nutritional Support for Thyroid Health
Selenium
Selenium is essential for the conversion of T4 to active T3, and for the selenoprotein enzymes that protect the thyroid from oxidative damage. Selenium supplementation has been shown in RCTs to reduce TPO antibody levels in Hashimoto's [2]. Brazil nuts (2 per day) provide approximately 100 to 200mcg selenium; supplemental selenium selenomethionine at 200mcg daily is the clinical form.
Iodine
Iodine is a structural component of thyroid hormones. Deficiency causes hypothyroidism; excess can worsen Hashimoto's. Dietary sources (seafood, seaweed, iodised salt, dairy) are preferred over high-dose supplementation in autoimmune thyroid conditions.
Zinc and Iron
Both zinc and iron are required for thyroid hormone synthesis and conversion. Deficiency in either impairs thyroid function independently of TSH levels.
Gluten and Thyroid Autoimmunity
There is a well-established association between Hashimoto's and coeliac disease, and a clinical association between gluten sensitivity and thyroid antibody levels. A gluten elimination trial is a standard clinical consideration in Hashimoto's management.
Gut Health
The gut-thyroid connection is significant. Intestinal permeability is a prerequisite for autoimmunity according to Fasano's model. Healing the gut is therefore central to any autoimmune thyroid protocol.
Suspected thyroid dysfunction that isn't being picked up on standard testing?
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References
• Caturegli P, et al. Hashimoto thyroiditis: clinical and diagnostic criteria. Autoimmunity Reviews. 2014;13(4-5):391-397. PubMed
• Toulis KA, et al. Selenium supplementation in the treatment of Hashimoto's thyroiditis: a systematic review and a meta-analysis. Thyroid. 2010;20(10):1163-1173. PubMed
