Inhibition of naloxone-stimulated adrenocorticotropin release by alprazolam in myotonic dystrophy patients

RARE POMC MUTATION IN A PATIENT WITH MYOTONIC DYSTROPHY TYPE 1 AND ADRENOCORTICOTROPIN HYPERRESPONSE TO CORTICOTROPIN-RELEASING HORMONE

Objective

Myotonic dystrophy (DM) is a monogenic disorder. It is caused by expansion of a cytosine-thymineguanine triplet in the DMPK gene which encodes for myotonic dystrophy protein kinase (DMPK).

Methods

A 24-year-old man with DM and the DMPK mutation presented with elevated adrenocorticotropic hormone (ACTH) levels twice (152 and 185 pg/mL; normal value is 10 to 52 pg/mL) with normal cortisol levels (134.6 and 113.0 ng/mL, or 371.3 and 311.7 nmol/L; normal values are 67 to 226 ng/mL or 184.8 to 623.5 nmol/L). ACTH, corticotropin-releasing hormone (CRH) and insulin tolerance test (ITT) demonstrated normal cortisol response to ACTH and partial response to CRH and ITT tests, and ACTH hyperresponse to CRH and ITT. We suspected ACTH and/or ACTH receptor (ACTHR) mutations and evaluated the genetic profile for pro-opiomelanocortin (POMC), melanocortin 2 receptor (MC2R) and follicle-stimulating hormone receptor (FSHR) genes.

Results

No mutations were found in either the MC2R or FSHR genes. The patient was heterozygous for the c.614A>G mutation corresponding to a p.53D>G substitution with a glycine instead of an aspartate in position 53 in POMC gene. This mutation was outside the sequence for ACTH (which spans amino acids 138 to 176) but was included in the part originating the N-terminal peptide of pro-opiomelanocortin (also called pro-γ-melanocyte stimulating hormone) which spans amino acids 27 to 102 and is involved in the regulation of adrenal steroidogenesis.

Conclusion

The pathologic expansion of the cytosine-thymine-guanine triplet repeat in the 3' noncoding region of DMPK could explain the hyperresponse of ACTH typical of DM. The mutation of pro-γ-melanocyte-stimulating hormone could be associated with the abnormal response of cortisol, compatible with a partial adrenal insufficiency. Other studies are necessary to demonstrate this hypothesis.

Cortisol response to diazepam: its relationship to age, dose, duration of treatment, and presence of generalized anxiety disorder

OBJECTIVE

Acute diazepam administration has been shown to decrease plasma cortisol levels consistent with decreased activity of the hypothalamic-pituitary-adrenal axis, especially in individuals experiencing stress. However, the effects of chronic diazepam treatment on cortisol have been less studied, and the relationship to age, anxiety, duration of treatment, and dose are not well understood.

METHOD

This double-blind placebo-controlled study examined acute and chronic effects of diazepam on plasma cortisol levels in young (19-35 years) and elderly (60-79 years) individuals with and without generalized anxiety disorder (GAD). Subjects received single oral challenges of placebo or diazepam (2.5 mg or 10 mg) in a placebo-controlled cross-over design, followed by 3 weeks of chronic daily treatment with 2.5 mg or 10 mg diazepam or placebo taken at 10 p.m., and then by a final acute challenge with a single oral dose of the same study medication received during chronic treatment.

RESULTS

The elderly experienced significant reductions in plasma cortisol levels compared to placebo both in the initial challenge and during chronic treatment, but the young did not. However, cortisol response to drug was comparable in both groups. Final challenge did not produce any significant cortisol effects in either group and the cortisol response in the elderly was significantly reduced compared to the initial challenge. GAD status was not a factor in plasma cortisol responses to diazepam.

CONCLUSIONS

Diazepam reduced cortisol both acutely and during chronic treatment, but not during final challenge, consistent with some tolerance development. This effect was most apparent in the elderly compared with the young adults and was not modulated by GAD status or dosage, and was not related to drug effects on performance and on self-ratings of sedation and tension.

Interdose elevation in plasma cortisol during chronic treatment with alprazolam but not lorazepam in the elderly

Benzodiazepines (BZPs) have been shown to reduce hypothalamic-pituitary-adrenal (HPA) axis activity acutely in normal humans. In contrast, the effects of chronic BZP treatment on the HPA axis have not been well studied, especially in the geriatric population. This study examined the acute and chronic effects (3 weeks) of alprazolam and lorazepam on plasma cortisol in 68 subjects (60-83 years) who received 0.25 or 0.50 mg b.i.d. alprazolam, or 0.50 or 1.0 mg b.i.d. lorazepam, or placebo orally according to a randomized, double-blind, placebo-controlled parallel design. Memory assessment and blood samples for plasma cortisol were obtained prior to the morning dose on days 0, 7, 14, and 21, and at 1, 2.5, and 5 h postdrug on days 0 and 21. Assessments of anxiety and depression were carried out at days 0, 7, 14, and 21 before drug administration. Plasma cortisol was affected compared to placebo only by the 0.5 mg alprazolam dose. During the first and the last day of treatment, there was a significant drop in cortisol at 2.5 h after alprazolam compared to placebo. The predose cortisol levels increased significantly during chronic alprazolam treatment, and correlations were found between these cortisol changes and changes in depression, anxiety, and memory scores. These findings suggest that even a short period of chronic treatment with alprazolam, but not lorazepam, may result in interdose HPA axis activation in the elderly, consistent with drug withdrawal. If confirmed, this effect may contribute to an increased risk for drug escalation and dependence during chronic alprazolam treatment.

Stimulatory and inhibitory regulators of the hypothalamo-pituitary-adrenocortical axis

Short- and long-term metabolic effects of stress are mediated through the hypothalamo-pituitary-adrenocortical (HPA) axis and the sympathetic nervous system. While efficient functioning of these systems is essential for life processes, dysfunction can lead to hypercortisolaemia and inappropriately elevated catecholamines, resulting in immunosuppression and associated pathologies. This review will concentrate on the central mechanisms involved in the control of HPA axis activity, particularly neuronal, neuropeptide and transcriptional input to CRF and AVP expression in the hypothalamus. The emphasis of the article will be on our increased understanding of selective and specific responses of the HPA axis to different types of stressors. Elucidating the biochemical mechanisms underlying stress may permit the development of pharmacological strategies to treat chronic stress which exacts such a major toll on our quality of life today.