Hypothyroidism-induced macroorchidism: use of a gonadotropin-releasing hormone agonist to understand its mechanism and augment adult stature

VanWyk-Grumbach syndrome in a male pediatric patient: A rare case report and literature review

Primary hypothyroidism usually leads to retardation of linear growth and delay or even arrest of puberty in juvenile patients. In rare cases, pediatric patients with hypothyroidism may present with signs of VanWyk-Grumbach's syndrome (VWGS), which includes juvenile hypothyroidism, delayed bone age and pseudoprecocious puberty. The present study reported on a rare case of VWGS and other complications, including obesity, short stature, hepatomegaly and pituitary hyperplasia. In addition, a comprehensive literature review was performed to illustrate the treatment and outcome of VWGS in pediatric patients. The present study contributed to the current knowledge regarding the diagnosis and treatment of VWGS in pediatric patients.

Pituitary Hormone Secretion Profiles in IGSF1 Deficiency Syndrome

BACKGROUND

Loss-of-function mutations in immunoglobulin superfamily member 1 (IGSF1) cause an X-linked syndrome of central hypothyroidism, macroorchidism, delayed pubertal testosterone rise, variable prolactin deficiency and variable partial GH deficiency in childhood. The clinical features and gene expression pattern suggest a pivotal role for IGSF1 in the pituitary, but detailed knowledge on pituitary hormone secretion in this syndrome is lacking. We therefore aimed to study the 24-hour pituitary hormone secretion in male patients with IGSF1 deficiency.

METHODS

We collected blood samples every 10 min for 24 h in eight adult male IGSF1-deficient patients and measured circulating TSH, prolactin and gonadotropins. Deconvolution, modified cosinor and approximate entropy analyses were applied to quantify secretion rates, diurnal rhythmicity and regularity of hormone release. Results were compared to healthy controls matched for age and body mass index.

RESULTS

Compared to healthy controls, IGSF1-deficient patients showed decreased pulsatile secretion of TSH with decreased disorderliness and reduced diurnal variation. Basal and pulsatile secretion of FSH was increased by over 200%, while LH secretion did not differ from healthy controls. We observed a bimodal distribution of prolactin secretion, i.e. severe deficiency in three and increased basal and total secretion in the other five patients.

CONCLUSION

The altered TSH secretion pattern is consistent with the previously hypothesized defect in thyrotropin-releasing hormone signaling in IGSF1 deficiency. However, the phenotype is more extensive and includes increased FSH secretion without altered LH secretion as well as either undetectable or increased prolactin secretion.

The role and potential sites of action of thyroid hormone in timing the onset of puberty in male primates

Puberty in primates is first delayed by a neurobiological switch that arrests pulsatile GnRH release during infancy and then triggered, after a protracted period of juvenile development, by resurgence in intermittent release of this hypothalamic peptide. The purpose of this chapter is to review recent studies conducted in our laboratories to begin to examine the role of thyroid hormone (TH) in governing this postnatal development of pulsatile GnRH release in primates and therefore the timing of puberty in these species. The male rhesus monkey was used as the experimental model and TH activity was manipulated by surgical and chemical thyroidectomy on the one hand, and by thyroxine (T(4)) and triiodothyronine (T(3)) replacement on the other. Our results indicate that the resurgence in pulsatile GnRH release at the termination of the juvenile phase of development is dependent on a permissive action of TH. Whether this action of TH is mediated directly on hypothalamic centers regulating the pulsatile release of GnRH, or indirectly by circulating signals reflecting TH action on somatic development remains to be determined.

Cullen's sign and massive ovarian enlargement secondary to primary hypothyroidism in a patient with a normal FSH receptor

Ovarian hyperstimulation is a recognised complication of longstanding hypothyroidism. A 12 year old girl with atrophic thyroiditis who presented with abdominal pain and distension is reported. She was noted to have bruising in the vicinity of the umbilicus (Cullen's sign). She had pronounced ovarian enlargement on ultrasonography and it was hypothesised that this profound phenotype might reflect an abnormal FSH receptor. However sequencing of the FSH receptor was normal. The ovarian enlargement resolved with thyroxine replacement. Physicians and surgeons should consider longstanding hypothyroidism in patients presenting with Cullen's sign.