Autoimmune thyroid diseases are more common in patients with prolactinomas: a retrospective case-control study in an Italian cohort

Clinical course of autoimmune thyroid diseases in women with prolactinomas: Results from a prospective study in a single tertiary centre

INTRODUCTION

Several retrospective and cross-sectional studies have revealed a higher prevalence of autoimmune thyroid diseases (AITD) with a predominance of autoimmune hypothyroidism in prolactinoma patients compared to the general population. To date, we have no data on the clinical course of AITD in these patients. The aim of this prospective study was to assess the clinical course of AITD in female patients with prolactinomas compared to an age- and thyroid-risk factors-matched control group.

MATERIALS AND METHODS

The study population consisted of 144 females (71 patients/73 controls) who underwent approximately a 6-year follow-up. Physical examination, thyroid ultrasound and laboratory testing (measurement of antibodies to thyroglobulin, thyroid peroxidase, TSH-receptor; serum TSH and FT4 levels) were performed twice - at the baseline and at the follow-up visits.

RESULTS

AITD were diagnosed in 26.8% (n=19) of the patients and 9.6% (n=7) of the controls (p=0.007) at baseline visit. At the end of the follow-up (FU), these percentages increased to 33.8% (n=24) among the patients versus 12.3% (n=9) in the control group (p=0.002). Hypothyroidism was significantly more frequent in prolactinoma patients than in controls at the end of the study (19.7% vs. 4.1%; p=0.003). Two prolactinoma patients had hyperthyroidism at the baseline visit and restored euthyroid state with negative TSH-receptor antibodies during the follow-up. We did not observe hyperthyroidism in the control group. Among the hypothyroid subsets, the average daily levothyroxine dose at FU visit varied from 25 to 200mcg in the prolactinoma group compared to 25 to 50mcg in the control group.

CONCLUSIONS

Female patients with prolactinomas seem to be prone to autoimmune hypothyroidism. As a pathogenetic mechanism, we could suggest the selective immunomodulatory action of PRL predominantly on cell autoimmunity, complement activation and antibody-dependent cytotoxicity, resulting in earlier and more rapid progression of Hashimoto's thyroiditis towards hypothyroid state in genetically predisposed individuals.

Global prevalence and epidemiological trends of Hashimoto's thyroiditis in adults: A systematic review and meta-analysis

Objective

Although Hashimoto's thyroiditis is associated with cardiovascular disease and malignancy, the global status of Hashimoto's thyroiditis is not well characterized across regions. Our objective was to evaluate the prevalence and trends of Hashimoto's thyroiditis in adults in regions with different economic income levels around the world.

Methods

For this systematic review and meta-analysis, we searched PubMed, Embase, MEDLINE, Scopus, and Web of Science databases, and 48 random-effects representative studies from the inception to June 2022 were included without language restrictions to obtain the overall prevalence of Hashimoto's thyroiditis in adults worldwide. In addition, we stratified by time of publication, geographic region, economic level of the region of residence, gender, diagnostic method, etc.

Results

A total of 11,399 studies were retrieved, of which 48 met the research criteria: 20 from Europe, 16 from Asia, five from South America, three from North America, and three from Africa. Furthermore, there are two projects involving 19 countries and 22,680,155 participants. The prevalence of Hashimoto's thyroiditis was 7.5 (95%CI 5.7-9.6%), while in the low-middle-income group the prevalence was 11.4 (95%CI 2.5-25.2%). Similarly, the prevalence was 5.6 (95%Cl 3.9-7.4%) in the upper-middle-income group, and in the high-income group, the prevalence was 8.4 (95%Cl 5.6-11.8). The prevalence of Hashimoto's varied by geographic region: Africa (14.2 [95% CI 2.5-32.9%]), Oceania (11.0% [95% CI 7.8-14.7%]), South America and Europe 8.0, 7.8% (95% Cl 0.0-29.5%) in North America, and 5.8 (95% Cl 2.8-9.9%) in Asia. Although our investigator heterogeneity was high (I²), our results using a sensitivity analysis showed robustness and reliability of the findings. People living in low-middle-income areas are more likely to develop Hashimoto's thyroiditis, while the group in high-income areas are more likely to develop Hashimoto's thyroiditis than people in upper-middle-income areas, and women's risk is about four times higher than men's.

Conclusions

Global Hashimoto's thyroiditis patients are about four times as many as males, and there are discrepancies in the regions with different economic levels. In low-middle-income areas with a higher prevalence of Hashimoto's thyroiditis, especially countries in Africa, therefore local health departments should take strategic measures to prevent, detect, and treat Hashimoto's thyroiditis. At the same time, the hidden medical burden other diseases caused by Hashimoto's thyroiditis should also be done well.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier: CRD 42022339839.

An update on the pathogenesis of Hashimoto's thyroiditis

It is 70 years since Noel Rose embarked on his pioneering studies that lead to the discovery of autoimmune thyroiditis and the elucidation of Hashimoto's thyroiditis. This short review to honour his passing focuses on the developments in our understanding of the causes and pathogenesis of HT over the last five years. Recent genetic studies have reported heritability estimates for HT and associated diseases for the first time, and emphasised the complexity of the genetic factors involved, including monogenic forms of HT. Environmental factors continue to be elucidated, especially as a side effect of drugs which modulate the immune system therapeutically. Regarding pathogenetic mechanisms, multiple cytokine networks have been identified which involve the thyroid cells in a circuit of escalating proinflammatory effects, such as the expression of inflammasome components, and an array of different defects in T regulatory cells may underlie the loss of self-tolerance to thyroid autoantigens. Finally, a number of studies have revealed fresh insights into disease associations with HT which may have both pathological and clinical significance, the most intriguing of which is a possible direct role of the autoimmune process itself in causing some of the persistent symptoms reported by a minority of patients with levothyroxine-treated HT.

Myasthenia gravis presenting as bilateral pseudointernuclear ophthalmoplegia in a patient with an incidental prolactinoma

Myasthenia gravis (MG) is a rare and potentially dangerous autoimmune condition, which affects the acetylcholine receptors at the neuromuscular junction of skeletal muscle. MG's diverse symptomatology may readily masquerade as other neurological conditions, posing a diagnostic challenge to clinicians. We describe a 24-year old man who presented to the emergency department with a new onset internuclear ophthalmoplegia. After a series of investigations, we eventually arrived at a diagnosis of MG with pseudointernuclear ophthalmoplegia with an incidentally detected prolactinoma. We explore the literature regarding the pathophysiology of pseudointernuclear ophthalmoplegia, the link between prolactin and autoimmunity and the association between prolactinoma and MG.