This Quasi experimental study was conducted at a tertiary care hospital from September 2018-August 2019. Institutional Ethics Committee approval was obtained before commencement of the study (Ref.No. DMIMS (DU)/IEC/2018-19/7486) and a valid informed consent was taken from each study participant. Being a purposive study, the sample size were 30 patients of both genders between age group of 15-30 years old suffering from grade 3 and grade 4 acne vulgaris attending dermatology Outpatient Department (OPD). Sample size was estimated to be 30 using Open Epi software to detect a mean difference of 5 between pre and post-intervention values with 95% Confidence level, 90% power and assuming a 5% attrition.

A detailed history regarding age, sex, educational status, marital status, duration of acne vulgaris, personal history, family history, and treatment history was taken.

Inclusion criteria: Patients of both genders and age group 15-30 years old, having grade 3 and grade 4 acne vulgaris and patients who were willing to give consent for participating in the present study were included in the study.

Exclusion criteria: Patients suffering from any major systemic disease/s, uncontrolled medical or surgical illness, those who were a known case of hypothyroidism, hyperthyroidism, hypopituitarism or hyperpituitarism, pregnant or lactating or unconsenting patients were excluded from the study.

A detailed clinical examination of patients of acne vulgaris was done and assessment of acne vulgaris severity was done by using a standard system of grading [Table/Fig-1] [9].

All the enrolled patients were prescribed oral capsule Isotretinoin at 0.5 mg/kg/day at night time after a fatty meal.

A baseline serum thyroid function test which included serum T3, T4 and TSH was carried out by taking venous blood samples from the subjects after 8 hours of overnight fasting before starting the drug and the patients were asked to follow-up after 3 months of continued oral Isotretinoin therapy with repeat thyroid profile and for assessment of common side effects like lip cheilitis for which Isotretinoin Cheilitis Grading Scale (ICGS) was used [10].

Categorical variables in the results were presented in the form of number as well as percentage (%) while continuous variables were presented in the form of mean±SD and median. The analysis of statistics was performed using inferential and descriptive statistical methods while student’s paired t-test was used to assess the comparison between baseline thyroid profile values with that of three months after continued Isotretinoin administration. Software used in the analysis was Statistical Package for Social Sciences (SPSS) version 24.0 and level of significance was considered as p<0.05.

Twenty males and ten females (Total 30 of patients) were included in this study. Mean age of the cohort was 19.3±3.14 years (age range of 15-30 years). In this study, patients suffering from grade 3 (20 patients) and grade 4 (10 patients), also considered as severe forms of acne vulgaris were observed. Out of grade 4 acne patients, 8 were males and 2 were females. On the other hand, out of grade 3 patients, 12 were males and 8 were females.

In the present study, out of 30 patients 28 subjects (93.33%) experienced lip cheilitis while only 2 patients reported no such complaint. The onset of cheilitis was noted within three weeks of treatment and continued throughout the treatment period. The patients were adequately counselled about lip dryness prior to initiation of Isotretinoin. Skin dryness was reported by 11 (36.67%) patients after starting Isotretinoin. Patients were prescribed lip balms and moisturisers for above complaints.

Baselines mean value of serum T3 was 1.15 and after 3 months of Isotretinoin administration was 1.28. The mean difference was 0.12±0.40. Therefore, although the serum T3 values were raised as compared to baseline values, the difference was not significant (p-value- 0.095).

Baselines mean value of serum T4 was 7.4 and after 3 months of Isotretinoin administration was 7.73. The mean difference was 0.33±2.13 while p-value was 0.40 which was statistically not significant [Table/Fig-2].

Out of all the previous studies quoted, the one conducted by O Leary TJ et al., is in accordance to the present study where even after 12 weeks of continued Isotretinoin administration, they observed no change in thyroid function test. Similarly, in a study conducted by AL Saif et al., no significant change was observed in serum TSH levels while the free T4, thyroid anti peroxidase (Anti TPO) and Thyroglobulin levels remained unchanged despite 8 months of isotretinoin therapy in acne patients. Also, in majority of the studies it was observed that higher dose of Isotretinoin was administered as compared to the present study [Table/Fig-3] [2,5-8,11].

In the present study, out of 30 patients, 28 patients (93.33%) complained of lip cheilitis while 11 patients (36.67%) complained of skin dryness over face during their monthly follow-up visits. Known side effects of retinoids like altered differentiation and shedding of epidermis contributes to poor barrier function and photosensitivity which may lead to manifestations like lip cheilitis and skin dryness [12]. In the present study, the treatment duration was of three months as suggested in the study by Rao PK et al., where they inferred that three months of Isotretinoin administration is advisable for effective management of moderate to severe forms of acne which is in concordance to the present study [13].

Retinoids exert their effects on target cells by binding and activating nuclear retinoid receptors as Retinoic Acid Receptors (RARs) and Retinoid X Receptors (RXRs), which are members of steroid-thyroid hormone super family [14,15]. RXR selective retinoids are known to influence vitamin D and thyroid hormone responsive genes.

All the retinoids have affinity for atleast one (α, β, γ) or many receptors of the RAR or RXR or both families except Isotretinoin which does not bind to any receptor RAR or RXR. This may be the key mechanism which explains the lack of effect of Isotretinoin on thyroid function as observed in present study. It has been postulated by a study that isotretinoin may act as a pro-drug that is converted intracellularly to metabolites that are agonists for RAR and RXR nuclear receptors, this phenomenon has been poorly understood till date [16]. On the other hand, Bexarotene is selective for RXR receptor and is clinically used in the treatment of cutaneous T cell lymphoma. Bexarotene is associated with severe central hypothyroidism with high frequency, associated with marked reductions in concentrations of TSH and thyroxine [17].

Small sample size and short follow-up period were important limitations. Since the dosage and duration of Isotretinoin administered in the present study subjects was fixed at 0.5 mg/kg/day and three months, respectively, the effect of Isotretinoin at variable doses and time duration was not evaluated. Also, in the present study, total serum T3, total serum T4 and TSH were evaluated. While serum free T3 and free T4 which indicate more accurate serum hormone levels were not evaluated.

In the study, minor alterations in the levels of T3, T4 and serum TSH were observed but the difference was statistically not significant. Thus, it can be concluded that there was no significant effect observed on thyroid function test and Isotretinoin can be safely given upto three months. It is recommended that further studies need to be conducted to assess the effect of continued oral Isotretinoin on serum thyroid hormone levels in acne vulgaris patients at variable doses and for variable time duration. Moreover, action of other metabolites of Isotretinoin on nuclear receptors also needs further exploration.