Ocular changes in primary hypothyroidism

Ocular complications of diabetes mellitus in a pediatric population and proposals for screening and follow-up programs

Background

Diabetes mellitus (DM) is one of the world's greatest health emergencies of the 21st century. Ocular complications of DM are commonly chronic and progressive, but vision loss can be effectively prevented or delayed with early detection and timely treatment. Therefore, regular comprehensive ophthalmologic examinations are mandatory. Ophthalmic screening and dedicated follow-up for adults with DM are well established, whereas, there is no consensus on optimal recommendations for the pediatric population, reflecting the lack of clarity about the current burden of disease in this age group.

Objectives

To determine the epidemiology of ocular complications of diabetes and to assess optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) macular features in a pediatric population with DM. To review ophthalmological screening and follow-up plans for the diabetic pediatric population.

Design

Observational study.

Methods

Retrospective consecutive cohort study of all 165 diabetic patients (330 eyes) aged 0-18 years, examined between January 2006 and September 2018 at the Pediatric Department of 'S. Maria della Misericordia' Udine Hospital who underwent at least one complete ophthalmologic examination at the Ophthalmology University Clinic at the Udine Hospital. OCT and OCTA data were available for 37 patients (72 eyes, 2 excluded). The associations between ocular complications and selected potential risk factors were evaluated by univariate analyses.

Results

No patient had signs of ocular diabetic complications or any macular morphological or micro-vascular impairment, regardless of any potential risk factor. The prevalence of strabismus and refractive errors in the study group, was found to be similar to non-diabetic pediatric populations.

Conclusion

Screening and follow-up of ocular diabetic complications in children and adolescents could be performed less frequently than in adults with diabetes. There is no need to screen potentially treatable visual disorders in diabetic children earlier or more frequently than in the healthy children thus reducing time spent in hospital and permitting a better tolerance to medical examinations in diabetic pediatric patients. We described the OCT and OCTA patterns in a pediatric population with DM.

Association between Thyroid Function and Ocular Parameters

During development, thyroid hormones play an important role in eye development, while in adults, some pathological thyroid conditions can affect the normal functioning of the eyes. Thyroid eye disease is the most well-known eye pathology caused by a pathological thyroid condition. Few studies have investigated the association between ocular parameters and thyroid function. Thus, in this study, we aimed to examine whether thyroid activity affects ocular parameters. This cross-sectional study included 4633 healthy adults recruited within the 10,001 Dalmatians project of the Croatian Biobank. The plasma levels of thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), thyroglobulin (Tg), thyroglobulin antibodies (TgAb), and thyroid peroxidase antibodies (TPOAb) were measured by an immunoassay. We determined 20 ocular parameters for each participant (10 for each eye, including corneal radius, corneal thickness, anterior chamber depth, anterior chamber angle, lens thickness, posterior chamber length, axial length, intraocular lens power (IOL), spherical power, and cylinder power). Patients with hyperthyroidism had thicker corneas compared to euthyroid individuals. Corneal thickness was also negatively associated with plasma TSH levels. Intra-ocular lens power was higher in patients with clinical hypothyroidism, while spherical power was higher in euthyroid individuals with positive antibodies compared to euthyroid individuals. Intra-ocular lens power negatively correlated with fT4 levels, while spherical power positively correlated with TgAb, TPOAb, and Tg levels and negatively correlated with TSH levels. The anterior chamber angle was positively associated with plasma TSH levels and TPOAb levels and negatively associated with plasma fT4 levels. These findings suggest an interesting interplay between ophthalmic measures and thyroid status, detectable even in the general adult population.

T4-mediated rescue of aortic malformations in hypothyroid rats indicates maternal thyroid status can affect great vessel development

Pexacerfont is a corticotrophin-releasing factor subtype 1 receptor (CRF-1) antagonist developed for potential treatment of anxiety and stress-related disorders. In male rats, pexacerfont caused hepatic enzyme induction leading to increased thyroxine (T4) clearance. When administered to pregnant rats on gestation day 6 to 15, pexacerfont at 300 mg/kg/day (30× mean AUC in humans at 100 mg/day) produced similar effects on thyroid homeostasis with serum T4 and thyroid-stimulating hormone levels that were 0.3-0.5× and 3.3-3.7× of controls, respectively. At this dose, fetuses of pexacerfont-treated dams presented findings associated with maternal hypothyroidism including growth retardation and increased skeletal alterations. Additionally, there were unexpected great vessel malformations that were mostly derived from the 4th pharyngeal arch artery in 5 (4.3%) fetuses from 3 (15.8%) litters. The etiology was unclear whether the vascular malformations were related to insufficient thyroid hormones or another mechanism. To better understand this relationship, pregnant rats were implanted with a subcutaneous L-thyroxine pellet designed to provide a sustained release of T4 throughout organogenesis in rat embryos (GD 6 to 15; the dosing period of pexacerfont). T4 supplementation produced a near euthyroid state in pexacerfont-treated dams and completely prevented the fetal vascular malformations. These results suggest maternal T4 levels during organogenesis may have a role in great vessel morphogenesis associated with patterning and/or regression of pharyngeal arch arteries. Although previous clinical reports have speculated a potential relationship between thyroid hormone homeostasis and early cardiovascular development, this is the first report to experimentally demonstrate this relationship in great vessel morphogenesis.

The effect of salt supplements on thyroid hormones and quality of pregnancy in female hypothyroid rats

Background

The use of nutrient supplements along with medication to optimize the treatment of diseases yields desirable outcomes. Hypothyroidism causes abnormalities in cells, and organs, and induces gene expression changes. The use of salt supplements and vitamins considerably helps to treat hypothyroidism.

Objectives

To evaluate the effect of a food supplement containing iron, iodine, and folic acid on thyroid hormones changes as well as the quality and quantity of hypothyroid female rat's offspring.

Materials and Methods

In the current experimental study, 40 female rats were divided into six experimental and two control groups. The study was conducted in three phases. In the first phase, the role of a combinatory supplement along with levothyroxine to treat hypothyroidism by assessing T3, T4, and TSH hormones was investigated. In the second phase, the dose-depended effects of a combinatory supplement were investigated. Additionally, in the third phase, the quality and quantity of the next generation were measured in the hypothyroid female rats receiving the salt supplement.

Results

The plasma level of T3, T4 and TSH in hypothyroid rats receiving nutrient supplements indicated that the use of combinatory supplements along with levothyroxine could have desirable effects on the treatment of hypothyroidism to such an extent that the level of T3 and T4 hormones in the intervention group was significantly higher than that of the control group (P≤0.01). The second phase demonstrated that the desired effects of combinatory supplements on the serum levels of T3, T4, and TSH hormones were dose-dependent so that by increasing the dosage of supplementation, a significant decrease in the TSH level was observed (P <0.05), while T3 and T4 levels increased (P <0.01).The results of the third phase demonstrated that salt supplements could be effective in reducing the number of dead or preterm pups, and the use of mineral salts along with levothyroxine could promote a healthy birth.

Conclusion

Salt supplements have considerable effects on the health status of the offspring of hypothyroid rats, resulting in the birth of more healthy pups and reducing the rate of abortion or preterm births.

Autoimmune thyroiditis and central serous chorioretinopathy may have a relation

Autoimmune thyroiditis (AT) is an important cause of hypothyroidism, and central serous chorioretinopathy (CSCR) is an independent disease of the choroid and retina that leads to accumulation of fluid beneath the retina. While AT has been associated with multiple antibodies, CSCR is still regarded as idiopathic despite extensive research. We hypothesize a causative association between these 2 conditions on the basis of our experience of a case where both CSCR and AT presented simultaneously and depicted a parallel course. CSCR was documented with retinal imaging while AT was documented with serum antibody titers. Further, we discuss the possible mechanisms that may be involved in this intriguing association.

The interrelation between hypothyroidism and glaucoma: a critical review and meta-analyses

Data on the association between hypothyroidism and glaucoma are conflicting. We sought to shed light on this by conducting a critical review and meta-analyses. The meta-analyses were conducted in adherence with the widely accepted MOOSE guidelines. Using the Medical Subject Heading (MeSH) terms: hypothyroidism, myxoedema and glaucoma or intraocular pressure, case-control studies, cohort studies and cross-sectional studies were identified (PubMed) and reviewed. Using meta-analysis, the relative risk (RR) of coexistence of glaucoma and hypothyroidism was calculated. Based on the literature search, thirteen studies fulfilled the inclusion criteria and could be categorized into two groups based on the exposure. The designs of the studies varied considerably, and there was heterogeneity related to lack of power, weak phenotype classifications and length of follow-up. Eight studies had glaucoma (5757 patients) as exposure and hypothyroidism as outcome. Among these, we found a non-significantly increased risk of hypothyroidism associated with glaucoma (RR 1.65; 95% confidence interval [CI]: 0.97-2.82). Based on five studies (168 006 patients) with hypothyroidism as exposure and glaucoma as outcome, we found the risk of glaucoma to be significantly increased (RR 1.33; 95% CI: 1.13-1.58). Based on these meta-analyses, there seems to be an association between hypothyroidism and glaucoma, which does not seem to be the case between glaucoma and hypothyroidism. However, larger scale studies with better phenotype classification, longer follow-up and taking comorbidity and other biases into consideration are needed to address a potential causal relationship.

Investigation of the choroidal thickness in patients with hypothyroidism

Purpose:

The effect of hypothyroidism on the choroidal thickness (CT) was investigated in patients with subclinical hypothyroidism and overt hypothyroidism, and biochemically and clinically euthyroid patients receiving levothyroxine treatment. The patients were compared with healthy subjects.

Materials and Methods:

One eye of 71 hypothyroid and 22 healthy subjects between 20 and 40 years of age were included in this study. CT measurements were taken at the fovea and at 2 points that were 1500 μm nasal and temporal to the fovea using spectral-domain optical coherence tomography. Independent sample t-test's and was used for statistical analysis of the data.

Results:

The CT was significantly thicker in hypothyroid patients compared to healthy subjects (P values were 0.013 for subfoveal, 0.015 for temporal and 0.020 for nasal segments). The intraocular pressure (IOP) and body mass index (BMI) were also significantly higher in hypothyroid patients (P values were 0.021 and 0.003, respectively). There was not a statistically significant difference in the BMI and IOP measurements between healthy subjects and euthyroid patients (P > 0.05). However, there was a statistically significant difference in the subfoveal, temporal and nasal CT measurements between healthy subjects and euthyroid patients (P values were 0.006, 0.031 and 0.013, respectively).

Conclusions:

All subgroups of hypothyroid patients had thicker CT compared to healthy subjects. Euthyroid patients receiving levothyroxine treatment had lower IOP, BMI levels, and serum lipid levels than patients with subclinical hypothyroidism and overt hypothyroidism.

Optic Disc, Macula, and Retinal Nerve Fiber Layer Measurements Obtained by OCT in Thyroid-Associated Ophthalmopathy

Aim. To compare the measurements of retinal nerve fiber layer (RNFL), macula and optic disc parameters obtained by optical coherence tomography (OCT), and intraocular pressure (IOP) between the patients with thyroid-associated ophthalmopathy (TAO) and healthy controls. Methods. One hundred and thirty-two eyes of 66 patients with TAO and 72 eyes of 36 healthy controls were included in the study. Proptosis level was determined by Hertel exophthalmometer. Optic disc, peripapillary retinal nerve fiber layer, and macula parameters were measured by OCT. All measurements of the patients were compared with those of age- and sex-matched healthy controls. Results. No statistically significant difference was found between the patients with TAO and control group in terms of demographic characteristics (P > 0.05). Exophthalmometer measurements and IOP were higher in TAO group (P < 0.05). Mean macula thicknesses in TAO and control groups were 239.3 ± 29.8 μm and 246.6 ± 31.8 μm, respectively, and the difference between the groups was statistically significant (P = 0.000). TAO group had thinner inferior RNFL thickness and macular thicknesses (superior, inferior, temporal, and nasal) and higher disc area and C/D ratio when compared with the control group (P < 0.05). Conclusion. IOP, disc area, and C/D area ratio were higher in the patients with TAO and the thicknesses of macula and inferior RNFL were thinner when compared with healthy controls. This trial is registered with registration number at clinicaltrials.gov NCT02766660.

The ocular surface in thyroid diseases

PURPOSE OF REVIEW

The purpose of the present review is to describe recent insights into the pathomechanism of ocular surface impairment in the course of thyroid dysfunctions. The review focuses in particular on Graves' ophthalmopathy as the majority of the literature is published on this topic.

RECENT FINDINGS

Mechanical factors were thought, until now, to be the indirect causes of ocular surface function failure. In particular, eyeglobe bulging and upper eyelid retraction with consequent eyelid fissure width increase were mainly considered responsible for increased exposed area and ocular surface impairment. Recent evidence demonstrated that ocular surface tissues are direct targets for autoantibodies in either hypothyroid or hyperthyroid states. A set of tear protein biomarkers were identified and shown to have high diagnostic performance.

SUMMARY

New horizons can be displayed on the basis of these new findings, in particular, as referred earlier, Graves' ophthalmopathy diagnosis. A detailed slit-lamp examination and a careful medical history by validated questionnaires in patients with ocular surface discomfort symptoms are now recommended to investigate early manifestations of an underlying thyroid dysfunction. Ocular surface signs should also be included in professional guidelines. Autoantibody assays in tears and proteomic analysis of tear protein expression could be important further steps in early diagnosis and posttherapy control of thyroid dysfunction.