Premature thelarche

There are four patterns of PT development. Most patients have hypertrophy followed by complete loss of the excess breast tissue (51% of cases) or loss of most excess tissue, but some remains until puberty (36% of cases). Less commonly patients have ongoing patterns of thelarche: 9.7% suffer from a cyclic pattern where the size of the breast tissue varies over time, and 3.2% experience continual increase in tissue size.[1]

The main symptom of PT is enlarged breast tissue in infants. estrogen's role in PT, also leads to increased bone age and growth in some cases.[5] In PT these secondary symptoms are minimal: bone age only varies from actual age by a few months and growth velocity only slightly varies from the norm. Diagnostic tests will distinguish these PT secondary symptoms from the more severe bone aging and growth occurring in early CPP.[3]

PT is linked to increased sensitivity of the breast tissue to estradiol, an estrogen derivative, in certain prepubertal individuals.[1] Sporadic estrogen or estradiol production in the adrenal glands, follicles or ovarian cysts is also linked to the condition.[2][6]

Follicle Stimulating Hormone (FSH) is secreted from the anterior pituitary. FSH plays a key role in development, growth and puberty, thus it is suspected to play a role in PT. Gondotropin-releasing hormone (GnRH) stimulation testing in some patients with PT has shown a dominant response from FSH. This response is linked to active mutations in the FSH receptor and Gs-a subunit in PT. Genetic investigation indicated these mutations only account for few cases of premature PT.[2][7] PT may also be caused by transient partial activation of the HPG axis. Partial activation would release a surplus of FSH from the anterior pituitary without further disruption of the HPG axis.[6]

The consumption or exposure to certain endocrine disrupters have also been linked to PT.[2]

Pelvic ultrasounds are important in diagnosing CPP.[3] Patients with CPP have an increased ovary and uterus size. The ovary and uterus volume of CPP patients is similar to that of females undergoing puberty.[1] The pelvis ultrasound is problematic as a diagnostic, as there is not a specific cut-off for the uterine and ovary volumes that indicate the patient has CPP. Patients with PT should have a uterine and ovarian volume within the normal range for their age. Pelvic ultrasounds are a desirable diagnostic as they are non-invasive and easy to continually review. The pelvic ultrasound should be paired with biochemical tests to determine the presence of CPP.[3]

Biochemical tests study the hormone levels in patients. CPP patients have elevated LH levels and peak LH:FSH ratios when compared to PT patients. It is hard to use LH as a diagnostic for CPP, as the LH assay has varying sensitivity and specificity.[1] The GnRH stimulation test is the main diagnostic biochemical test used to distinguish PT from CPP.[3] The GnRH test demonstrates the pituitary responsiveness to GnRH. GnRH stimulates the release of LH and FSH from the anterior pituitary. The peak LH:FSH ratio in CPP patients is similar to the ratio of pubertal females. Females with PT demonstrated a LH:FSH ratio lower than pubertal females.[8] The disadvantages of the GnRH stimulation test is it takes a long time to perform and requires multiple collections from the patient, making the process time consuming and inconvenient. The test is highly specific but has low sensitivity as the LH hormone response is usually observed in later stages of CPP.[3] There are also overlaps in the expected value in the GnRH test results of individuals with CPP and PT.[1]

The diagnostic inconsistency in CPP means that a combination of all of pelvic ultrasounds and biochemical tests should be paired with observation, to ensure PT doesn’t progress to CPP.[1]

Natural commodities like fennel, lavender and tea tree oils have been linked to PT. Lavender and tea tree oil have weak estrogenic activities. These estrogenic properties may cause an imbalance in endocrine signalling pathways, leading to PT in regular users of these products.[1] Fennel tea has been studied as an endocrine disrupter linked to PT. Fennel seed oil contains anethole a compound with estrogenic effects. The tea contains fennel seed oil and regular use results in increased estradiol levels in the infant. Infants with fennel tea related PT, were given the tea as a homeopathic remedy for restlessness. The tea was consumed for at least four months before the presentation of PT symptoms. PT resulting from fennel tea subsides approximately six months after stopping the use of fennel tea.[9]

Leptin is an adipocyte hormone that has important implications of puberty and sex hormone secretion. Increased leptin has been linked to estrogen and estradiol secretion. Leptin has key roles in maintaining age appropriate body composition and desired weight. Leptin receptors are also found in mammary epithelial cells and leptin has been observed as a growth factor in breast tissue. Increased leptin levels have been observed in some cases of PT. The increase in leptin levels cause increased estradiol levels and development of breast tissue.[6]

The form of PT with fluctuating hypertrophy in patients has been linked to activating mutations in the GNAS1 gene. This mutation accounts for a small number of cases of PT.[5][7]