Article: Thyroid and HRT

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Article: Thyroid and HRT
Thyroid: Another Tangled Vine in the Hormone Jungle

Patricia Morse

THYROID AND ESTROGEN

The thyroid is a butterfly-shaped gland in your neck that produces hormones controlled by the pituitary gland. The pituitary sends out ThyroidStimulating Hormone (TSH) to tell the thyroid gland to produce thyroxine,which affects metabolism, heart rate, body heat, hair and skin growth, mood swings, periods, memory, and energy level (see symptoms listed below). Youcan see that estrogen and thyroid deficiencies are related! After beginning any estrogen therapy or after an oopherectomy, a woman should get tested for thyroid function.

Thyroxine, like estrogen, can be either bound (for storage) or free (for use) in the blood. Only the free hormone does anything (is biologically active). Estrogens increase thyroid binding (meaning that there is less for use), while androgens decrease thyroid binding. In addition, there is a complex feedback system of messages between the thyroid/pituitary and the ovaries that isn't totally understood yet. Menopause often brings on thyroid problems. Surgical menopause can only be more likely to create problems.

There are a series of tests to get a precise picture of what's happening.

Your thyroid should be monitored as you change your HRT. Changes in thyroid happen slowly, so wait at least 4 to 6 weeks after a change in your thyroid dose before testing again. Normal ranges can vary depending on the laboratory.

THYROID TESTS

TSH test (also called thyrotropin) If TSH is high, then your pituitary gland is sending out a lot of messenger signals. This shows that your thyroid is underactive (hypothyroid). It sends out a lot of messengers because it's not sensing enough T3 and T4 in the blood. TSH is useful for monitoring thyroid levels once you are under treatment, but other tests are needed to get a clear picture. Normal: 0.2 to 4.7 mcU/mL (microunits per milliliter). The higher the number, the more deficient.

Total T4 (tetriiodotyrosine, 80% of thyroxine, controls metablolism) This measures the level of actual hormone in your blood. It measures both bound and free hormone, and it is more sensitive than the TSH test, showing changes sooner. Normal: between 4.5 and 12.5 mcg/dL (micrograms per deciliter).

Free T4 index This measures the amount of thyroid hormone actually available for use in your cells. Normal: 0.8 to 1.9 ng/dL.

Total T3 (Triiodothyronine, 20% of thyroxine) This is the best test for hyperthyroidism (too much thyroxine in the blood). This is important if you are taking thyroid replacement so that it's clear whether your dose is too high. It responds independently of the T4 tests, so combinations of these tests should be done together. Normal: between 75 and 200 ng/dL (nanograms per deciliter)

Resin T3 Uptake This test is only useful with the Total T4 or Total T3 tests. It shows how much hormone is getting bound up as opposed to being produced. A high total T4 might be a result of too much hormone being produced or it might be the result of too much thyroid binding protein (like Thyroid Binding Globulin or TBG). If estrogen has increased the binding capacity, then the free hormone will be decreased and the resin T3 uptake will be decreased. Normal: 25% to 35%.

Antithyroid antibodies This tests for autoimmune diseases that affect the thyroid.

TBG Thyroid-binding globulin tests follow the other tests if the results don't make sense to the doctor. And if disease is found, there are of course CT scans, ultrasounds, and other imaging tests.

MAIN THYROID SYMPTOMS

Hypothyroidism (An underactive thyroid) Fatigue, exhaustion, feeling run down and sluggish, depression, unexplained or excessive weight gain, dry, coarse and/or itchy skin, dry, coarse and/or thinning hair, feeling cold, especially in the extremities, constipation, muscle cramps, hoarse or gravely voice, puffiness and swelling in the eyes and face, pains and aches in joints, hands and feet, carpal tunnel syndrome, mood changes, forgetfulness, snoring, long-lasting infections, tinnitus, dizzyness, light sensitive eyes (and the menstrual cycle is badly affected)

Hyperthyroidism (An overactive thyroid) Nervousness, irritability, increased perspiration, thinning of your skin, fine brittle hair, muscular weakness especially involving the upper arms and thighs, shaky hands, racing heart, more frequent bowel movements, weight loss despite a good appetite, lighter flow, less frequent menstrual periods

Sources: Jill Tongen (hystersister), Thyroid Foundation of America, Journal of Naturopathic Medicine, http://www.healthanswers.com, and the best thyroid website on the web, Mary Shomon's http://thyroid.about.com/health/thyroid/

This content was written by staff of HysterSisters.com by non-medical professionals based on discussions, resources and input from other patients for the purpose of patient-to-patient support.