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A complex relationship exists between thyroid and liver in health and disease. Liver plays an essential physiological role in thyroid hormone activation and inactivation, transport, and metabolism. Conversely, thyroid hormones affect activities of hepatocytes and hepatic metabolism. Serum liver enzyme abnormalities observed in hypothyroidism may be related to impaired lipid metabolism, hepatic steatosis or hypothyroidism-induced myopathy. Severe hypothyroidism may have biochemical and clinical features, such as hyperammonemia and ascites, mimicking those of liver failure. Liver function tests are frequently abnormal also in hyperthyroidism, due to oxidative stress, cholestasis, or enhanced osteoblastic activity. Antithyroid drug-associated hepatotoxicity is a rare event, likely related mainly to an idiosyncratic mechanism, ranging from a mild hepatocellular damage to liver failure. Propylthiouracil-induced liver damage is usually more severe than that caused by methimazole. On the other hand, thyroid abnormalities can be found in liver diseases, such as chronic hepatitis C, liver cirrhosis, hepatocellular carcinoma, and cholangiocarcinoma. In particular, autoimmune thyroid diseases are frequently found in patients with hepatitis C virus infection. These patients, especially if thyroid autoimmunity preexists, are at risk of hypothyroidism or, less frequently, thyrotoxicosis, during and after treatment with interpheron-alpha alone or in combination with ribavirin, commonly used before the introduction of new antiviral drugs. The present review summarizes both liver abnormalities related to thyroid disorders and their treatment, and thyroid abnormalities related to liver diseases and their treatment.

Purpose: According to a few recent studies, the clinical phenotype of Graves’ disease (GD) at onset is becoming milder in recent years, in terms of prevalence and severity of hyperthyroidism, goiter and overt eye disease. The aim of this study was to assess the change in GD phenotype across the late twentieth and the early twenty-first centuries. Materials and methods: We carried out a systematic search of studies published between 1/1/1980 and 12/31/2017 describing naïve GD patients at diagnosis. We collected epidemiological, clinical, biochemical and serological data reported in the selected studies, and (1) conducted a single-arm meta-analysis to compare clinical and biochemical characteristics of naïve GD patients before and after year 2000 and (2) performed a meta-regression to identify the trend of the observed clinical presentations. Results: Eighty selected articles were related to the period before the year 2000, 30 to the years 2000–2017. According to demographics, the two defined populations were homogeneous at meta-analysis: overall estimated female prevalence was 81% [95% CI 79–82], mean estimated age of the entire population was 39.8 years [95% CI 38.4–41.1], with no significant differences between pre- and post-2000 groups (p> 0.05). The overall estimated prevalence of smokers was 40% [95% CI 33–46], with no significant difference between the two groups (p> 0.05). Mean estimated free thyroxine (FT4) and free triiodothyronine (FT3) levels at diagnosis were higher in the pre-2000 group: 4.7 ng/dl [95% CI 4.5–4.9] for FT4 and 14.2 pg/ml [95% CI 13.3–15.1] for FT3, as compared to the post-2000 group: 3.9 ng/dl [95% CI 3.6–4.2] for FT4 and 12.1 pg/ml [95% CI 11.0–13.3] for FT3 (all p< 0.01). Goiter estimated prevalence was higher in the pre-2000 group, 87% [95% CI 84–90], than in the post-2000 group, 56% [95% CI 45–67]. Estimated prevalence for Graves’ Orbitopathy (GO) was 34% [95% CI 27–41] in the pre-2000 group and 25% [95% CI 19–30] in the post-2000 group (p= 0.03). Accordingly, meta-regression adjusted for covariates showed an average annual reduction of FT4 (− 0.040 ± 0.008 ng/dl, p< 0.0001), FT3 (− 0.316 ± 0.019 pg/ml, p< 0.0001), goiter prevalence (− 0.023 ± 0.008%, p= 0.006), and goiter size (− 0.560 ± 0.031 ml, p< 0.0001). Conclusions: Our meta-analysis and meta-regression confirmed that GD phenotype at diagnosis is nowadays milder than in the past; we hypothesize that conceivable factors involved in this change are iodoprophylaxis, worldwide decrease in smoking habits, larger use of contraceptive pill and micronutrient supplementation, as well as earlier diagnosis and management.

Antithyroid drugs (ATDs) are first-line treatment for Graves’ hyperthyroidism worldwide, but relapses are frequent. The reliability of individual risk factors to predict at baseline subsequent relapse is poor. Predictive scores grouping single risk factors might help to select the best treatment (pharmacological vs. ablative). To assess the predictivity of a recently developed score (Clinical Severity Score, CSS) and to compare it with another score (GREAT score). A retrospective observational, single-center study was conducted of 387 consecutive, newly diagnosed Graves’ patients, who completed an 18–24 months ATD course and were followed for at least 2 years. Hyperthyroidism relapsed in 185 patients (48%). At diagnosis and before treatment, the relapse group had higher serum TSH-receptor antibody and free thyroxine levels and larger goiters than the remission group, with no differences in Graves’ orbitopathy prevalence and severity. In the multivariate analyses, only large goiter size was significantly associated with an increased recurrence hazard ratio. Using CSS, the risk of relapse increased from 36% in the mild category and 49% in the moderate category to 59% in the severe category, with quite a good area under the curve (AUC) (0.60; 95% CI: 0.55; 0.66). GREAT score showed an increase in relapse from 34% for class I (mild) and 49% for class II (moderate) to 64% for class III (severe) (AUC, 0.63; CI: 0.58; 0.68). Both CSS and GREAT score are useful, although imperfect, tools to predict at baseline relapse of hyperthyroidism after treatment. In real life they may help the clinician to tailor a treatment for newly diagnosed Graves’ hyperthyroidism.