A direct role for thyroid hormone in development of the adrenal cortex

Delayed pubarche

In healthy adolescents, delayed pubarche is generally a benign condition that is caused by a physiological discrepancy between gonadarche and adrenarche. In presence of other clinical signs and symptoms, delayed pubarche can be caused by single or multiple hormones deficiency (such as adrenal insufficiency, panhypopituitarism and hypothyroidism) and/or genetic conditions (Turner syndrome, androgen insensitivity syndrome). Exposition to endocrine disruptors has also been described as a possible cause of delay of pubic hair development. Basic blood tests, karyotype and first level imaging studies are helpful in the differential diagnosis.

Adrenal androgens, adrenarche, and zona reticularis: A human affair?

In humans, reticularis cells of the adrenal cortex fuel the production of androgen steroids, constituting the driver of numerous morphological changes during childhood. These steps are considered a precocious stage of sexual maturation and are grouped under the term "adrenarche". This review describes the molecular and enzymatic characteristics of the zona reticularis, along with the possible signals and mechanisms that control its emergence and the associated clinical features. We investigate the differences between species and discuss new studies such as genetic lineage tracing and transcriptomic analysis, highlighting the rodent inner cortex's cellular and molecular heterogeneity. The recent development and characterization of mouse models deficient for Prkar1a presenting with adrenocortical reticularis-like features prompt us to review our vision of the mouse adrenal gland maturation. We expect these new insights will help increase our understanding of the adrenarche process and the pathologies associated with its deregulation.

RNA-Seq Reveals Sub-Zones in Mouse Adrenal Zona Fasciculata and the Sexually Dimorphic Responses to Thyroid Hormone

The sex-specific prevalence of adrenal diseases has been known for a long time. However, the reason for the high prevalence of these diseases in females is not completely understood. Mouse studies have shown that the adult adrenal gland is sexually dimorphic at different levels such as transcriptome, histology, and cell renewal. Here we used RNA-seq to show that in prepubertal mice, male and female adrenal glands were not only sexually dimorphic but also responded differently to the same external stimulus. We previously reported that thyroid hormone receptor β1 (TRβ1) in the adrenal gland is mainly expressed in the inner cortex and the fate of this TRβ1-expressing cell population can be changed by thyroid hormone (triiodothyronine; T3) treatment. In the present study, we found that adrenal glands in prepubertal mice were sexually dimorphic at the level of the transcriptome. Under T3 treatment, prepubertal females had 1162 genes differentially expressed between the saline and T3 groups, whereas in males of the same age, only 512 genes were T3-responsive. Immunostaining demonstrated that several top sexually dimorphic T3-responsive genes, including Cyp2f2 and Dhcr24, were specifically expressed in the adrenal inner cortex, precisely in an area partially overlapping with the X-zone. Under T3 treatment, a unique cortical layer that surrounds the adrenal X-zone expanded significantly, forming a distinct layer peculiar to females. Our findings identified novel marker genes for the inner adrenal cortex, indicating there are different sub-zones in the zona fasciculata. The results also highlight the sex-specific response to thyroid hormone in the mouse adrenal gland.

Adrenal steroids in female hypothyroid neonates: Unraveling an association between thyroid hormones & adrenal remodeling

CONTEXT

The adrenal gland undergoes significant remodeling during the neonatal period, an essential developmental process that still remains incompletely understood. With respect to control over the remodeling process and, specifically, the role of thyroid hormones (TH), no human studies have been published. The effect of both hypo- and hyper-thyroidism has only been evaluated in adults, focusing on the mature adrenal. Recently, Huang et al identified expression of the TH receptor β1 in the mouse adrenal X-zone and demonstrated that TH administration could alter the postnatal adrenal remodeling process.

OBJECTIVE

To address whether TH influence adrenal steroid profiles and adrenal remodeling during the neonatal period.

METHODS

We compared the adrenal steroid profile of a naturally occurring prototype, female neonates with severe congenital hypothyroidism (CH, n=22, upon diagnosis of CH), with that of euthyroid neonates (n=20).

RESULTS

Significantly higher levels of adrenal steroids (17-OH-progesterone, DHEAS, Δ4- androstenedione and testosterone) were measured in neonates with severe CH compared to euthyroid neonates, returning within normal range after euthyroid state had been established on L-thyroxine replacement therapy whereas cortisol levels did not differ. TSH values in the CH group were positively, while FT4 levels were negatively correlated with circulating adrenal steroids.

CONCLUSIONS

The hormonal profile of female neonates with severe CH suggests a more active adrenal fetal zone than controls. These data indirectly associate TH with the adrenal remodeling and maturation process in humans. Based on our results we suggest that severe hypothyroidism decelerates the involution of the adrenal fetal zone that normally occurs postnatally.