Isolated thyroid-stimulating hormone deficiency

What it is

From: Orphanet

A type of central congenital hypothyroidism, a permanent thyroid deficiency that is present from birth, characterized by low levels of thyroid hormones due to a deficiency in TSH synthesis.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormal circulating thyroglobulin concentration · Very frequent (99-80%)

Any deviation from the normal concentration of thyroglobulin in the blood circulation.

Decreased circulating thyroxine level · Very frequent (99-80%)

A reduction below the normal concentration of thyroxine in the blood. Thyroxine (also known as T4) is the main hormone secreted by the thyroid gland into the blood. It can be converted into the active form triiodothyronine (also known as T3).

Decreased thyroid-stimulating hormone level · Very frequent (99-80%)

Reduced amount of the thyroid-stimulating hormone (TSH), which is produced by the anterior pituitary gland and stimulates the function of the thyroid gland.

Increased pituitary glycoprotein hormone alpha subunit level · Very frequent (99-80%)

An increased concentration of circulating alpha polypeptide of glycoprotein hormones (NCBI Gene 1081). This alpha subunit is common to luteinizing hormone (LH) , follicle stimulating hormone (FSH) , thyroid stimulating hormone (TSH) and human chorionic gonadotropin (hCG), which are glycoprotein hormones composed of an identical alpha subunit together with a beta subunit that confers biological specificity. The alpha subunit is used as a marker for tumors that produce these hormones.

Pituitary hypothyroidism · Very frequent (99-80%)

A type of hypothyroidism that results from a defect in thyroid-stimulating hormone secretion.

Reduced radioactive iodine uptake · Very frequent (99-80%)

A decreased amount of uptake on the radioactive iodine uptake (RAIU) test, which utilizes a radioisotope of iodine to measure how much iodine the thyroid gland absorbs from the blood. The radioactive marker is measured 4-6 hours and in some cases also 24 hours after administration of the radioactive marker.

Thyroid hypoplasia · Very frequent (99-80%)

Developmental hypoplasia of the thyroid gland.

Abnormality of epiphysis morphology · Frequent (79-30%)

An anomaly of epiphysis, which is the expanded articular end of a long bone that developes from a secondary ossification center, and which during the period of growth is either entirely cartilaginous or is separated from the shaft by a cartilaginous disk.

Constipation · Frequent (79-30%)

Infrequent or difficult evacuation of feces.

Delayed cranial suture closure · Frequent (79-30%)

Infants normally have two fontanels at birth, the diamond-shaped anterior fontanelle at the junction of the coronal and sagittal sutures, and the posterior fontanelle at the intersection of the occipital and parietal bones. The posterior fontanelle usually closes by the 8th week of life, and the anterior fontanel closes by the 18th month of life on average. This term applies if there is delay of closure of the fontanelles beyond the normal age.

Delayed proximal femoral epiphyseal ossification · Frequent (79-30%)

Developmental delay of ossification of the proximal epiphysis of the femur.

Delayed skeletal maturation · Frequent (79-30%)

A decreased rate of skeletal maturation. Delayed skeletal maturation can be diagnosed on the basis of an estimation of the bone age from radiographs of specific bones in the human body.

Depressed nasal bridge · Frequent (79-30%)

Posterior positioning of the nasal root in relation to the overall facial profile for age.

Dry skin · Frequent (79-30%)

Skin characterized by the lack of natural or normal moisture.

Other findings in the same source

From: Orphanet

Additional reported features include Failure to thrive (Frequent (79-30%)); Fatigue (Frequent (79-30%)); Feeding difficulties in infancy (Frequent (79-30%)); Growth delay (Frequent (79-30%)); Hoarse voice (Frequent (79-30%)); Hypercholesterolemia (Frequent (79-30%)); Hyporeflexia (Frequent (79-30%)); Hypothermia (Frequent (79-30%)); Increased circulating prolactin concentration (Frequent (79-30%)); Large posterior fontanelle (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Infancy; Neonatal

Inheritance in the source

From: Orphanet

Autosomal recessive

Understanding the inheritance label

From: MedlinePlus Genetics

An autosomal recessive pattern usually involves disease-causing changes in both copies of a gene. Parents may each carry one altered copy without having the condition themselves. A genetic counsellor can explain carrier testing and reproductive implications using the actual laboratory findings, rather than the condition name alone.

Which doctor should you see?

The suggested department for discussing Isolated thyroid-stimulating hormone deficiency is Endocrinology, with a endocrinologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which hormone or metabolic finding is important in this case?
• How should test timing and current medicines be taken into account?
• What follow-up would show whether the care plan is working?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Isolated thyroid-stimulating hormone deficiency. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.