Armour Thyroid Hair and Skin Changes: What the Evidence Actually Shows

What Armour Thyroid Contains

Armour Thyroid is desiccated thyroid extract, made from dried, ground animal thyroid glands, usually porcine [6]. Its labels state 38 mcg of levothyroxine (T4) and 9 mcg of liothyronine (T3) per 60 mg grain [4]. That is roughly 4.2 parts T4 to 1 part T3, compared with about 14:1 for the hormones the human thyroid gland secretes, so the tablet carries relatively more T3 and can produce serum T3 levels above the normal range shortly after a dose [5]. FDA states that animal-derived thyroid medications are not FDA approved, and the Armour Thyroid label says the product has not been approved by FDA as a new drug [6][4].

What the Crossover Trials Measured

Hoang and colleagues (Journal of Clinical Endocrinology and Metabolism, 2013) randomized 70 adults aged 18 to 65 with primary hypothyroidism, all stable on levothyroxine for 6 months, to 16 weeks of desiccated thyroid and 16 weeks of levothyroxine in a double-blind crossover [2]. There were no differences in symptoms or neurocognitive tests [2]. Patients weighed 3 lb less on desiccated thyroid (172.9 vs 175.7 lb, P<0.001), and 34 patients (48.6%) preferred desiccated thyroid, 13 (18.6%) preferred levothyroxine and 23 (32.9%) had no preference [2].

In a 22-week crossover study (Shakir 2021), 75 patients received levothyroxine, levothyroxine plus liothyronine, and desiccated thyroid [1]. TSH stayed in range in all treatment arms, and there were no differences in the symptom questionnaire, quality of life, memory or depression scores apart from a minor heart-rate increase on desiccated thyroid [1]. Neither trial lists hair or skin among its reported outcomes [1][2].

Hair and Skin in FDA's Recall Notice

FDA's September 2020 recall notice for two subpotent lots of NP Thyroid lists hair loss and dry skin among the signs and symptoms of hypothyroidism that patients may experience if they receive a subpotent product [3]. That notice concerns NP Thyroid, not Armour Thyroid. The Armour Thyroid label's adverse reactions section says reactions other than those of hyperthyroidism from overdosage are rare, and it does not state whether Armour Thyroid itself causes hair loss [4].

What the Label Uses to Judge Whether Replacement Is Adequate

The label says the dose must be individualized according to patient response and laboratory findings, and that adequate therapy usually produces normal TSH and T4 levels after 2 to 3 weeks [4]. It lists a usual starting dose of 30 mg with increments of 15 mg every 2 to 3 weeks, with most patients needing 60 to 120 mg/day, and a lower 15 mg/day start when long-standing myxedema or cardiovascular impairment is suspected [4]. The label gives no conversion factor from levothyroxine [4]. It also advises stopping biotin at least 2 days before assessing TSH and/or T4, because biotin can make TSH, T4 and T3 immunoassay results inaccurate [4].

The Practical Answer

The trials do not establish that desiccated thyroid improves hair or skin compared with levothyroxine. The American Thyroid Association's 2014 guideline recommends levothyroxine in preference to thyroid extracts, a strong recommendation based on moderate-quality evidence [5], and FDA states that professional society guidelines recommend synthetic levothyroxine as the preferred treatment [6].